Just the basics: Assessing the availability of supermarket budget ranges

Executive Summary

How are consumers coping with soaring food prices?

• Food inflation is at the highest rate in over 45 years, with prices rising by 19.2% in the year to March 2023. 
• Consumers are adapting their habits to meet the challenge of rising prices, including by switching supermarkets, buying cheaper items and looking for special offers. But for those already struggling to make ends meet, there has been little respite from rising prices. In February 2023, one in six (15%) people reported skipping meals.

What can supermarkets do to help?

• Supermarkets, as the place where most people do most of their grocery shopping, are on the frontline of this crisis. Which?’s Affordable Food for All campaign has called on supermarkets to step up and do more to support people through the current crisis - and target support particularly to those who are struggling the most. 
• As part of this, it’s essential that supermarkets provide a basic range of budget lines across their stores to support healthy choices, especially in places where people are most likely to need support to avoid poor quality diets and, as our research increasingly shows, hunger. 
• This report presents a rigorous audit of the extent to which Asda, Morrisons, Sainsbury's and Tesco are offering basic budget line essentials across their stores, including in high priority places - places we have identified as where people are most likely to struggle to access affordable food. Using mystery shoppers, we explored the availability of a basket of around 29 essential budget range items in 123 stores across the UK.

Our findings

• Consumers face a situation of extremes depending on which type of supermarket store they rely on. Supermarket stocking of our budget basket is generally good in large stores, where our mystery shoppers were on average able to find shelf-edge tickets for nine in ten items on our list. 
• However, consumers who rely on small local supermarket stores will almost never be able to buy the essential budget line items on our list. Of the 35 small Tesco, Sainsbury's and Morrisons stores we visited, 30 did not have in stock any of the listed budget line items at all. In each of the other five small stores, our mystery shoppers were only able to find a single budget line item from our list in stock. This means the budget line items on our list were available less than 1 per cent of the time.
• The lack of these budget lines in small stores limits the option of trading down to cheaper products for people who rely on this type of store. This is likely to make it harder for people with personal mobility issues, without access to a car, with poor access to public transport, and those on lower incomes, who are more likely to rely on convenience stores to access affordable, healthy food. In a March 2023 survey, we found that 66% of those on less than £21,000 per year shop in a smaller store at least once a week. 
• We found no difference in the availability of our budget range basket between high and low priority places - i.e. places where people are more or less likely to struggle to access affordable food. A closer look at store size reveals that this is consistent with our broader findings: while mid-large and very large supermarkets have good stock levels of budget lines in both high and low priority places, small stores are no more likely to stock our budget basket in places where people are more likely to struggle to afford food. This puts consumers with personal mobility issues, and those who lack access to private or public transport, at a particular disadvantage. 
• Budget line items, like other groceries, are sometimes out of stock. We found that in very large stores consumers were on average able to buy 25 of the 29 items on our list of essentials, falling to 24 in mid-large stores. The items most likely to be missing included staples like minced meat and tinned tuna. The non-budget alternatives to these items are usually significantly more expensive, meaning lack of availability could leave families going without.

 Our recommendations for supermarkets

• Supermarkets have a crucial role supporting people during the current cost of food crisis - and particularly helping people in the places around the country where they are most likely to be struggling. 
• Supermarkets are now providing a wide range of budget lines that will support a healthy diet in their larger stores, but they need to put a much greater focus on their small, convenience stores. Small stores need to offer a basic and healthy range of budget lines so that this option is available for the growing number of people who are having to trade down who may not be able to access larger stores. We found this to be an issue with Tesco, Sainsbury’s and Morrisons who have established small stores, and as Asda rolls out its new convenience stores, it also needs to ensure that this is addressed.
• This is particularly important in those areas where people are struggling the most - and so supermarkets need to prioritise the stores that they have in high priority places, ensuring that they offer an adequate and healthy range of essential budget lines that meet the needs of the local community. The Priority Places for Food Index provides a tool to help them identify these areas where people are likely to be most in need. 
• More generally, supermarkets need to ensure that their pricing is clear and transparent, including for promotions and loyalty card offers, so that people are able to easily compare products and decide which is the best value for their needs.

Introduction 

Food prices are rising rapidly

UK food prices are rising at the fastest rate in over 45 years. In March 2023, the annual inflation rate for food and non-alcoholic beverages hit 19.2% [1]﹘ a severe shock to the system after a decade of low food inflation, illustrated in Figure 1.

Figure 1: Food inflation soared in the last 12 months 

Prices have risen across all categories, but inflation is particularly high for milk, cheese, eggs, oils and fats. A range of factors have driven food prices higher, including global commodity price hikes, higher energy prices, supply chain disruption, and the Russian invasion of Ukraine.

Paying the price 

Consumers are doing their best to manage the challenges posed by rising prices. Members of our Consumer Insight panel tell us that they have been switching supermarkets, batch cooking, choosing own-brand products, and purchasing fewer fresh items to try to make their cash go further [2].

“I’m definitely eating out less, and probably batch cooking a bit more, getting more frozen stuff. I'm not getting fresh fruit and veg [anymore], I'm getting vegetables that I can put in the freezer.” Which? Consumer Insight panel member

This echoes survey research we conducted in August 2022 which found that even earlier in the cost of living crisis households were making significant adjustments to their spending habits. The vast majority of people (85%) told us that they were trying to do something to save money on food, with the most common changes being looking for items on promotion (55% of consumers), trading down to cheaper products (50% of consumers) and less regularly buying expensive or treat foods (42%), as shown in Figure 2 [3].

Figure 2: Consumers are trying to manage the cost of living by buying special offers, trading down and skipping treats

However, many people on lower incomes were already taking these steps to manage their budgets before the crisis, meaning when prices rose, there was little room to cut back. That has left people facing empty plates or turning to food banks [4]. Just over a quarter of consumers (27%) said they had gone without some foods due to rising costs in our February Consumer Insights tracker, and one in six (15%) said they had skipped meals [5].

These rising prices will affect all UK households, but will be disproportionately challenging for those on lower incomes, who spend more of their budgets on food and drink. Our recent analysis has suggested that retired and single parent households are the hardest hit [6].

Our Priority Places for Food Index, developed in partnership with the University of Leeds, draws on data from seven different domains, looking at both the extent to which people in a local area are likely to need affordable food and their access to it to explore where across the UK people are at greatest risk of food insecurity [7]. In high priority places, people are more likely to be living on lower incomes, and while some consumers have adapted to the crisis by shopping around, people in high priority places are less likely to have this option due to fewer supermarkets nearby and poorer access to transport.

These local areas tend to be concentrated; we found 95 Westminster constituencies where at least half of local areas in the constituency are in the bottom quintile of the Priority Places for Food Index, and 16 constituencies where at least three quarters of local areas are priority places, illustrated in Figure 3 [8].

Figure 3: High priority places are concentrated in the Scottish central belt, the Welsh Valleys, North East England, Yorkshire and the West Midlands

How are supermarkets helping?

People struggling to afford food are seeking support from a range of sources. The government undoubtedly has an important role at the central, national and local level supporting people through this crisis. People will also be turning to local charities and community groups. However, the fundamental role of supermarkets in the UK’s grocery market means that these businesses have a key role to play in supporting consumers.

In November, Which? launched its Affordable Food for All campaign, calling for supermarkets to do more to support people who are struggling to access affordable food. This included a call on supermarkets to provide a basic range of essential budget lines to support healthy, everyday choices, available across all stores, but particularly in high priority places, where people are most likely to need support to maintain a healthy diet and avoid hunger.

Although supermarkets may be unable to stock as many products in small stores, they should be able to provide a basic range of essential budget products, especially in the areas where people are struggling most to afford food. Consumers thought this was the one of the most important things that supermarkets could do, with 36% saying that having more budget range foods available would help them to save the most money on food in supermarkets [10].

In this report, we present new rigorous research undertaken to explore the extent to which the UK’s major traditional supermarkets are offering a range of basic budget line essentials to customers across their stores, particularly in high priority places. Using mystery shoppers, we explored the availability of a basket of essential items across stores of varying sizes in a range of locations.

Methodology

To assess the extent to which households are able to access a range of healthy, affordable budget range items in supermarkets, we put together a list of essential items, including fresh, frozen and tinned fruit and vegetables, meat and cheese, and store cupboard essentials like baked beans, tinned tuna, dried pasta and teabags. Our basket was informed by the basket used by the ONS to track the prices of the lowest-cost everyday grocery items, which itself was built from data on the foods low income households purchase the most. Our list was then sense checked by experts at Which? and the University of Leeds [11]. The list was limited to an average of 29 items per store, as this was assessed in pilot testing to achieve balance between being thorough and keeping the task manageable for our mystery shoppers. The basket for each supermarket varied slightly to account for variations in budget ranges. A full description of the baskets can be found in the Annex.

Mystery shoppers visited stores of Asda, Morrisons, Sainsbury's and Tesco in a range of locations across the UK. These brands were assessed as they are the major supermarkets following a traditional model, typically offering a range of price points and brands for different items, including specific budget lines, which makes our question about budget lines pertinent in a way that it isn’t in discount stores which offer a much smaller range of products and engage in more limited brand proliferation [12] [13].

The list of stores visited was developed carefully to ensure that for each supermarket chain we visited stores across a range of high, medium and low priority places, of different sizes and with different levels of local competition [14]. We were unable to visit small Asda stores as they have only recently started to offer these and store numbers across the country are low [15]. In total, 123 stores were visited by our mystery shoppers. To allow for variation in stocking due to delivery schedules, each store was visited at least twice, and usually three times, at different times of day and days of the week, giving us a total dataset of 358 supermarket visits. 

Our mystery shoppers were asked to look carefully for each item on the list, and note whether:

a. A shelf-edge ticket was present, indicating that the item is included in the store’s range, even if it is currently out of stock and unavailable.
b. The item itself was on the shelf, indicating that it is in stock and available to buy.

To make the exercise as realistic as possible, where fruit and vegetable budget range items were not available, shoppers were asked to see if there was an alternative budget range item available. The item was then marked as in stock in our results. This reflects a generous assumption that if a particular vegetable is out of stock, cash-strapped consumers may be more likely to switch to another vegetable in the budget line rather than buy a more expensive alternative.

This report

In Section 2, we present the findings of our mystery shopping exercise. 

Section 3 presents our recommendations to supermarkets for how they can better support their customers through the worst food inflation in 45 years. 

A full methodology is provided in the Annex.

Research findings

To understand the patterns of budget line availability across the country, we analysed the data collected by our mystery shoppers in several different ways. First, we assessed budget line availability by store size. We also identified which items were most likely to be missing, assessed stocking levels between high and low priority places for food, and analysed the results of our audit by brand of supermarket. The results of this analysis show where supermarkets could be doing more to help consumers, particularly those on lower incomes, to access affordable, healthy food.

Small stores almost never sell any of our budget range basket

We found that the availability of our budget line basket was generally good in mid-large and very large stores across all four supermarkets. Our mystery shoppers were able to find shelf-edge tickets for 96% of the items in our basket on average in very large stores, and for 93% of items on average in mid-large stores [16].

However, in small Morrisons, Sainsbury’s and Tesco stores we found a very different story, with budget line items very rarely available, even in the places where people are most likely to be struggling to access affordable food [17].

Of the 35 small stores from these three chains visited across the country by our mystery shoppers, 30 did not have in stock any of the budget range items on our basic list at all. In each of the five stores where a budget range item from our list was in stock, they had only one of the items in our basket. This means the budget line items on our list were available less than 1 per cent of the time.

This is concerning given that our recent Which? survey revealed that two-thirds (66%) of consumers on lower incomes rely on small convenience stores for their essential shopping needs, with at least one or sometimes several visits each week [18]. When asked why they depended on these small stores people often said they were “essential for daily supplies” such as vegetables or bread.

By not adequately stocking budget range necessities in their small stores, supermarkets are leaving consumers who only have access to smaller stores, due to personal mobility issues, lack of access to a car, poor access to public transport or poor internet access, less able to access affordable, healthy food. Worryingly, these people are more likely to be living on lower incomes, meaning they can ill afford the higher priced items exclusively offered in small stores [19].

This is most likely to be causing consumers problems in high priority places, where access to transport may be more limited. Being within walking distance was a common response in our survey for why people on low incomes depend on convenience stores - “They’re close to my home. The big supermarket requires a car or bus journey to get to” with another consumer admitting they “don’t have a car” and so can’t access larger stores [20].

Our sample of stores visited included three high priority places where more than half of supermarkets are small stores - Don Valley, in Yorkshire, North West Durham, in the North East, and Rhondda, in Wales [21] [22]. Across these three constituencies, we made 12 visits to four small stores [23]. None of the items on our list of budget essentials was available in any of these stores. As high priority places, consumers in these constituencies are more likely to struggle to access transport that would let them access larger stores, and to be living on lower incomes. Together, this suggests that some of these people will be relying on these small stores, and so unable to access affordable, healthy budget line items which would help them manage the cost of living crisis. A similar picture is likely to play out in other high priority places across the country.

While we understand that with limited space in small stores, supermarkets must make difficult decisions about ranging, the lack of budget lines in small stores in high priority places risks causing consumers financial difficulty and contributing to hunger. 

The very poor availability of budget items from our list in small stores would have distorted all our further analysis of this data, consistently dragging median availability values across stores down in a way that would not have been representative of true budget line availability in mid-large and very large stores. For this reason, we chose to exclude small stores data from the rest of our analysis, allowing us to give an accurate description of budget line availability in mid-large and very large stores.

Availability of budget lines is good in high priority places, in large stores 

Continuing our priority place analysis, we found better news for mid-large and very large stores. 

When we looked at the availability of budget items on our list across mid-large and very large stores in high, medium and low priority places, we found no significant differences. Stores in areas where people are more likely to need support to access affordable food had the same levels of availability of our budget basket as those in low priority places, where people are less likely to struggle to access affordable food. Mid-large stores in high and low priority places had approximately 86% and 85% of items in our basket in stock and available to buy respectively when the mystery shoppers visited, and the proportion of items where edge-of-shelf tickets were available was also statistically indistinguishable between high and low priority places, at 93%. 

This means that the Asda Brynmawr Superstore, in the high priority constituency of Blaenau Gwent in Wales, had virtually the same stocking of our essential budget items as the Asda Clapham Junction Superstore in the low priority constituency of Battersea in London. Equally, the Tesco Bradford Superstore, in high priority Bradforth South, had the same stock of budget range essentials as the Tesco Bridlington Superstore in low priority East Yorkshire. Morrisons Doxford Park Sunderland, in high priority Houghton and Sunderland South, had very similar stocking of our list to Morrisons Lutterworth in low priority South Leicestershire. While Sainsbury's Heaton Park, in high priority Blackley and Broughton, had a very similar stocking level of our basket to Sainsbury's Longwater in low priority South Norfolk.

These examples were hand-picked from our sample, but should broadly apply across the country and across supermarkets. 

This is important because, while we are pleased to see stores in high priority places have decent stock of our budget range essentials, this only applies to larger stores. As we saw previously, small stores lack any availability of the essential budget items we investigated. We would hope and expect that consumers with the greatest need of budget range items would be prioritised in the stocking or restocking or budget items - whether it is in large or small stores.

What’s most likely to be missing? 

We next examined what items shoppers were most likely to struggle to find in mid-large and very large stores. 

Although stocking was generally good, in some cases budget range items weren’t actually available to buy, despite a shelf-edge ticket. In very large stores, on average 87% of items were in stock, and in mid-large stores this fell to 84%. In practice, that means that on average in very large stores consumers would usually only be able to buy 25 of the 29 essential healthy budget items on our list, falling to 24 in mid-large stores.

Looking across all four big brands, we found minced meat, tuna and ketchup were the least likely to be in stock on average [24].

Figure 4: Mince meat and tinned tuna were the least likely to be in stock on average across all mid-large and very large stores

Not having budget ranges available can hit consumer budgets particularly hard, as more premium brands can be significantly more expensive. This is likely to be especially true in small stores where stock of our budget line essentials is likely to be very poor.

As well as some items that were consistently less likely to be in stock, we found some items that stores were the most likely to be in stock across the board, listed in Figure 5, and were particularly pleased to see two types of vegetable in this list, helping households to make healthy choices on a tight budget.

Figure 5: Tinned tomatoes and tinned vegetables were the most consistently in stock budget-range essentials

This reflects a wider theme that the availability of fruit and vegetables was generally good across mid-large and very large stores. Our budget range basket included nine items of fresh, frozen and tinned fruit and vegetables. Across our sample of mid-large and very large stores, we found that 86% of the budget fruit and vegetable items were in stock and available to buy, despite well-publicised challenges with fresh produce availability at the time of fieldwork, suggesting that supermarkets may be prioritising the availability of budget line fruit and vegetables to consumers. We were pleased to see this result, which will enable people facing financial challenges to continue making healthy choices, avoiding worsening existing health inequalities [26].

While all of the stores tested had broadly even budget line availability, Asda tended to perform slightly better than the other brands. We were particularly impressed by Asda’s commitment to ensuring that their budget lines are listed for sale in stores; our mystery shoppers were able to identify a shelf-edge label for the budget range items on our list 97% of the time in their stores, and found items in stock nine times out of ten - significantly higher than any other supermarket [27]. Morrisons also scored highly at 96% for shelf-edge tickets, but their in stock levels were slightly less good [28]. Tesco and Sainsbury’s, even in large stores, consistently had essential budget items from our list that were not routinely stocked, determined by the lack of a shelf-edge ticket. Budget range items only bring benefit when they’re available on the shelves, and where items on a basic shopping list are not stocked, this will limit the choice of consumers on a tight budget.

Figure 6: Asda performed best in having the highest stock of budget-range essentials on our list available

Conclusions

In mid-large and very large stores, supermarkets generally scored well against our audit. Most budget lines from our list that would enable a healthy diet were available to consumers. 

However, stock of essential budget range items on our list in the small Tesco, Sainsbury’s and Morrisons stores we visited was effectively nonexistent, even in high priority places where we know people are most likely to struggle to access affordable food. This puts consumers with personal mobility issues, and those who lack access to private or public transport, at a particular disadvantage. 

And although budget line availability in mid-large and very large stores was generally good, there is still room for improvement. Looking across brands, Asda are to be congratulated for consistently offering their budget ranges to customers in store, with shelf-edge tickets for the items on our list identified in 97% of cases. The other supermarkets have more to do to make sure the budget lines they offer are actually on the shelves for customers to buy, even in mid-large and very large stores.

Our recommendations 

Our research shows that many people are finding it increasingly difficult to afford food and having to make some very difficult choices. The government has a crucial role providing a nutritional safety net and ensuring that people are adequately protected.

Supermarkets, however, also have a vital role, given that they are the main place that most people buy their food in the UK. Our Affordable Food For All campaign has highlighted the important support they can provide by ensuring that affordable ranges are available, targeting their promotions so they support people most in need and by providing clear and transparent pricing.

This research shows that when it comes to provision of affordable ranges, supermarkets are falling short in terms of making the budget ranges they have developed available to people who have to shop in their small stores. In contrast, a range of essential budget range items were readily available in the larger stores across all four of the supermarket chains we looked at, showing that they do have a wide mix of products available within their budget ranges. Based on the mix of products that we included in our basket, it should be possible to opt for products within these ranges and be able to eat healthily.

Our consumer research has found that availability of budget ranges is important to people in the current crisis. Providing more budget ranges was the top action that people wanted from supermarkets to help them save money on food and more than half (56%) of those finding their finances very difficult said that they would benefit from more budget ranges being available [30].

• Supermarkets therefore need to focus on increasing the availability of budget lines within their small convenience stores. We found this to be an issue with Morrisons, Sainsbury’s and Tesco, and as Asda rolls out its new convenience stores it also needs to ensure that this is addressed. While it will not be possible to provide as wide a range of products as within their larger stores, it should still be possible to include a mix of products that support a healthy diet and which are appropriate for the local community.
• Priority should initially be given to improving budget range availability in the places where people are at greatest risk of food insecurity. The Priority Places for Food Index enables supermarkets to identify where they have stores, including small, convenience stores, within the priority places where support is most needed around the UK.
• More generally, supermarkets need to ensure that their pricing is clear and transparent, including for promotions and loyalty card offers, so that people are able to easily compare products and decide which is the best value for their needs.

Annex: Detailed methodology

To conduct this study, Which? worked with the specialist agency Mystery Shoppers to audit the availability of a range of budget items designed to support a healthy diet across the four largest supermarkets using a traditional business model in the UK: Asda, Morrisons, Sainsbury's and Tesco.

These brands were assessed as they are the major supermarkets following a traditional model, typically offering a range of price points and brands for different items, including specific budget lines, which makes our question about budget lines pertinent in a way that it isn’t in discount stores which offer a much smaller range of products and engage in more limited brand proliferation [31] [32].

We conducted the research in 123 stores chosen at random from across the UK. Each store had three visits, except 11 which had only two, from shoppers totalling 358 visits. In each store shoppers looked for an average of 29 items (varying by store). To allow for variation in stocking due to delivery schedules, each store was visited at least twice, and usually three times, at different times of day and days of the week, giving us a total dataset of 358 supermarket visits. Fieldwork was conducted 21 February - 24 March 2023.

We would like to thank the work of everyone at Mystery Shoppers, including the fieldworkers, without whom this study would not have been possible.

Store selection criteria

We used a stratified random sampling framework with stores chosen to create a broadly even balance between:

• Supermarket (Asda, Morrisons, Sainsbury's, Tesco)
• Store size (small, mid-large, very large)
• Whether they were within a high, medium or low priority places
• Local competitive environment

To identify store size we used the roof size as a proxy, the data for which was provided by Geolytix. Small stores have a roof size less than 280m2, mid sized stores between 280m2 and 1,400m2, large stores between 1,400m2 and 2,800m2 and very large stores over 2,800m2. For ease of analysis we then combined mid and large stores to create the mid-large category used throughout the analysis. The values reported here are medians and the boundaries are the same as used in the Priority Places for Food Index. Asda has very few small stores in the UK and so we did not include any small Asda stores in our study. The small stores referred to are made up of a balanced number of Morrisons Daily, Tesco Express and Sainsbury's Local stores (see figure 7 below).

To identify whether stocking of budget items varied across places according to the likelihood that people there are struggling to access affordable food, we used the Priority Places for Food Index, developed in partnership with the University of Leeds, to identify high, medium and low priority constituencies, referred to as priority places in this report. If the distribution of local areas in the bottom quintile of the index were evenly spread we would expect each constituency to have 20% of their local areas in the bottom quintile. However instead they are highly concentrated in some constituencies and non-existent in others. To understand the impact of this concentration we sampled from the top, middle and bottom of the constituency distribution. High priority places are defined as constituencies with 75% or more of their local areas in the bottom quintile of the priority places for food index. Medium priority places are constituencies with 40-50% of their local areas in the bottom quintile and low priority places are constituencies with no local areas in the bottom quintile.

To assess the local competitive environment the Proximity to Supermarket Retail Facilities domain from the Priority Places for Food Index is used as a proxy. This domain includes data on average distance to nearest large grocery store (Geolytix Retail Points v15) and the average count of stores within 1km (Geolytix Retail Points v15). A lower decile means there are relatively fewer retail facilities in the local area and thus lower local competition. We define higher competition as areas in deciles 7 to 10; and lower competition as areas in deciles 1 to 6. 

Combining the above factors, we then selected stores at random from across the UK to ensure a broadly even balance across these factors. 

Figure 7 provides details of the stores visited using our stratified random sampling framework.

Figure 7: Breakdown of stores visited by supermarket

Creating the basket of goods

To assess the extent to which households are able to access a range of healthy, affordable budget range items in supermarkets, we put together a list of essential items, including fresh, frozen and tinned fruit and vegetables, meat and cheese, and store cupboard essentials like baked beans, tinned tuna, dried pasta and teabags. Our basket was informed by the basket used by the ONS to track the prices of the lowest-cost everyday grocery items and sense checked by experts at Which? and the University of Leeds [33]. The ONS offers a list of 30 key everyday grocery items; our changes to this were to replace unhealthy items, like chips, with healthy alternatives and improve the representation of fruits and vegetables (fresh, tinned and frozen) in the basket. The list was limited to an average of 29 items, as this was assessed in pilot testing to achieve balance between being thorough and keeping the task manageable for our mystery shoppers.

Wherever possible the same items were selected for each supermarket. Where this was not possible, we chose the closest substitute available. If no close substitute was available then that item was excluded from the basket for that store. For instance, because of the variation in the budget ranges across supermarkets, we asked shoppers to look for beef mince at Asda, pork mince at Tesco, pork and beef mince at Morrisons and we did not include mince at Sainsbury's because they did not have a budget-range equivalent available at the time of fieldwork. Because of this variation in the budget ranges of supermarkets, the size of the basket for each supermarket varies slightly, but averages 29 items.

Of the average 29 items, nine were fruit and vegetable items, which included fresh, prepared, frozen and tinned. The products chosen were selected in the aim of having consistency across stores.

To ensure the research was as realistic as possible, for fruit and vegetable items we asked shoppers to find alternatives if the named item was out of stock. This is based on the generous assumption that cash-strapped shoppers would seek a closely related budget-range alternative, if their preferred fruit or vegetable was out of stock. The potential alternatives shoppers looked for were taken from a defined list of up to four we provided. If the alternative was in stock, the item was marked as in stock in our results. For example, we asked Tesco shoppers to look for Rosedene Farms Small Apple 6 Pack, but if this was out of stock then we asked them to look for one of the following: Rosedene Farms Braeburn Apples 6 Pack, Perfectly Imperfect Pears 800G, Rosedene Farms Small Pear Pack 550G, Suntrail Farms Orange Minimum 5 Pack. We did not ask shoppers to seek alternatives for all items for two reasons: first, to emphasise the need for healthier choices in the essentials basket. Second, to limit the effective size of the basket and ensure relative simplicity for the shoppers.

A full list of items mystery shoppers were asked to look for can be seen in Figure 8.

Figure 8: Full list of items provided to shoppers

Data collection, quality and assurance

We asked shoppers to provide us with the following data for each item: 

• Whether a shelf-edge label was visible (for both when an item was in and out of stock)
• The price listed (if a label was visible)
• An approximation of the amount of stock of the item available (0, 1-9, 10-29, 30+)
• Their subjective assessment of whether the item was easy or hard to find and reach
• Photographs of the items and relevant section of aisles for quality checking

To verify the data, Which? and Mystery Shoppers conducted several checks:

• Mystery Shoppers conducted manual checking of shoppers’ data using photographs taken by shoppers.
• Which? conducted further quality checking, including sense checking of stock and ranging levels, sensitivity testing across store visits and some manual checking of photographs.
• Where we identified systemic issues with data accuracy, we removed these instances. In the data set we excluded:
  • Some instances of JUST ESSENTIALS by Asda Cheese & Tomato Pizza 314g. The weight marked was for frozen, not fresh, pizza and some shoppers found the wrong item. To test this we used the prices provided by shoppers. At the time of fieldwork the Asda Cheese and Tomato chilled pizza was £1.05. We removed all instances (n=9) where the shopper’s price did not match our stated price. We also conducted manual checking of photographs to ensure accuracy.
  • Some instances of JUST ESSENTIALS by Asda Sliced Carrots 300g. The categorisation of this item was inaccurately provided to shoppers. In the vast majority of instances shoppers found an alternative, accurate, fresh vegetable which we retained. Where they said they had found the incorrect sliced carrots, we removed these from the data (n=19).
  • All instances of Morrisons Savers Beef & Pork Mince 750g (n=94). This item had an unusually low level of availability, with only 6 shoppers locating a shelf edge label and it being in stock only once. After investigating using the photographs provided by shoppers, we concluded that the shoppers who did find the item or its shelf-edge ticket had made mistakes except in one case. For quality assurance, we removed all instances of this item. It appears that since the design of this work, this item may have been discontinued.
  • All instances of Morrisons Savers No Added Sugar Squash (n=94). Only one shopper claimed to have found a shelf edge ticket for this item and this shopper was the only shopper to claim the item was in stock. After investigating using the photographs provided, it appears they made a mistake. It appears this item may have been discontinued since fieldwork design. As such, we removed all instances.
• During fieldwork there was also a national shortage of fresh vegetables which led to some supermarkets limiting the amount of stock customers could buy. As we allowed for inclusion of replacement items, where possible, for fruits and vegetables, the impact of the shortage on our results would have been kept to a minimum. We carefully monitored the situation alongside the agency Mystery Shoppers, and checked our results to monitor whether any fruits or vegetables had systematic stocking issues, and found no evidence the shortage adversely affected our results. 

Data analysis

Due to variation in the budget ranges across supermarkets (see Figure 8) and in the removal of some data (see data quality and assurance above), there was some variation in baskets between visits. Given this variation, proportionate scores are based on the basket size on each visit, rather than using a single basket size over the whole study. This ensured our scoring was accurate and fair to each supermarket and to each individual store.

In order to get a measure of availability which was not overly affected by outliers, our availability scores here are based on the median of all observations in a given store. 

All figures were subject to quality assurance to ensure accuracy and consistency of results. Data manipulation and summaries were performed using Python pandas 2.0 [34]. Significance testing (T-test, ANOVA, Chi-Squared) was conducted with Python Scipy 1.10 [35].

March 2023 survey methodology

Online survey conducted by Yonder Consulting on behalf of Which?. The survey was conducted 24-26 March 2023 with a panel of 2,086 UK adults and the results were weighted to be nationally representative.

Citation

If citing this paper in your own work, our preferred citation is: Jooshandeh, J., Di Marcello, T. and Davies, S., Just the basics: Assessing the availability of supermarket budget ranges, Which?, April 2023.

Footnotes

[1] Office for National Statistics (2023) Recent trends in UK food and drink producer and consumer prices: January 2023  ↑

[2] Which? (2023) How are consumers adjusting to the Cost of Living Crisis?  ↑

[3] Which? Cost of Living Food survey (2022). Base: All respondents (n=2791). Survey conducted 8–9 August 2022. For further details please see: https://www.which.co.uk/policy-and-insight/article/consumers-in-a-food-cost-crisisaqXGl6y4CPYl/  ↑

[4] House of Commons Library (2022) Food bank demand and the rising cost of living  ↑

[5] Which? (2023) Financial wellbeing in February 2023  ↑

[6] Which? (2023) Inflation and Household Spending - January 2023  ↑

[7] Consumer Data Research Centre (2023) Priority Places for Food Index  ↑

[8] The local areas are LSOAs (Lower Super Output Areas) in England and Wales, Data Zones in Scotland (2011 boundaries) and Super Output Areas in Northern Ireland. These small areas are designed to be of a similar population size. In England and Wales, LSOAs have an average of approximately 1,500 residents or 650 households. Data Zones in Scotland are smaller with around 800 people on average, while we estimate that Super Output Areas in Northern Ireland have an average of around 2,000 people  ↑

[9] In the relatively small number of cases in which a local area falls into multiple Westminster constituencies, these have been matched using a best-fit approach. Local areas are matched to the constituency where the highest proportion of the local area’s population falls into. The population estimates are based on the city and town classification analysis  ↑

[10] Which? Cost of Living Food survey (2022). Base: All respondents (n=2791). Survey conducted 8–9 August 2022  ↑

[11] Office for National Statistics (2022) Tracking the price of the lowest-cost grocery items, UK, experimental analysis: April 2021 to September 2022  ↑

[12] By Kantar market share, as of April 2023  ↑

[13] The Guardian (2019) The Aldi effect: how one discount supermarket transformed the way Britain shops  ↑

[14] For further information on how these are defined, please see the Annex  ↑

[15] Asda (2022) Asda launches first ‘Asda Express’ convenience stores  ↑

[16] See annex for detail on how we determined store size  ↑

[17] Asda is excluded from this part of the analysis as they have only recently introduced convenience stores, and very few are currently open, meaning we were not able to include them in our sample  ↑

[18]  Survey conducted with 2,086 UK adults by Yonder on behalf of Which? (24-26 March)  ↑

[19] House of Lords Library (2022) Cost of living: Impact of rising costs on disabled people. NatCen (2019) Transport and Inequality: An evidence review for the Department of Transport  ↑

[20]  Survey conducted with 2,086 UK adults by Yonder on behalf of Which? (24-26 March)  ↑

[21] Defined through our Priority Places for Food Index (see introduction and Which? (2022) Affordable Food for All: How supermarkets can help in the cost of food crisis)  ↑

[22] In these three constituencies, at least half of all food retailers listed on Geolytix are small stores, and at least half of the stores operated by Asda, Morrisons, Sainsburys and Tesco are small stores. Brands listed on Geolytix are Aldi, Asda, Amazon, Booths, Budgens, Dunnes Stores, Farmfoods, Heron, Iceland, Lidl, Makro, M&S, Morrisons, Planet Organic, Sainsburys, Spar, Tesco, Co-op, Waitrose and Whole Foods Market. We exclude stores that are linked to hospitals, airports, train and service stations, outlet stores, wholesalers (Costco and Makro) and home stores. (59% and 57% respectively. The store location data is from Geolytix Version 26 as at November 2022  ↑

[23] In Don Valley we visited a Sainsbury's Local and Tesco Express, in North West Durham we visited a Tesco Express and in Rhondda we visited a Morrisons Daily  ↑

[24] Morrisons Savers Tuna Chunks In Brine 145g was never in stock in our data set though a shelf-edge ticket was present on 94% of visits (excluding small stores). The product appears to have since been discontinued, according to the Morrisons website, however as the item had some presence in stores during our data collection period, we chose to retain this data in the analysis as a realistic representation of our mystery shoppers’ experiences. Tesco Stockwell & Co Tomato Ketchup 540G was also never in stock in our data set, though a shelf-edge label ticket was present on 83% of visits (excluding small stores). The product appears to have since been discontinued, according to the Tesco’s website, however as the item had some presence in stores during our data collection period, we chose to retain this data in the analysis as a realistic representation of our mystery shoppers’ experiences  ↑

[25] For data quality, we removed all instances of Morrisons Savers Beef & Pork Mince 750g and Morrisons Savers Squash and some instances of Asda Cheese & Tomato Pizza and Asda Carrots. For a full explanation of our data quality process, please see the Annex. Sainsbury's did not have a budget range mince or tuna at the time of fieldwork design and so are excluded from this analysis. All in stock and shelf-edge label statistics for visits and supermarkets have been adjusted accordingly  ↑

[26] Dimbleby, H. (2020) The National Food Strategy: Part One  ↑

[27] Difference to Morrisons is statistically significant, p value = 0.013  ↑

[28] For Asda and Morrisons some data was removed in the quality checking and assurance process. See Annex for details  ↑

[29] Small stores are excluded from this analysis, as Asda has very few small stores across the country, and we were unable to include any of these in our sample. Scores were adjusted to reflect the number of items searched for in that store and visit  ↑

[30] Which? Cost of Living Food survey (2022). Base: All respondents (n=2791)  ↑

[31] By Kantar market share, as of April 2023  ↑

[32] The Guardian (2019) The Aldi effect: how one discount supermarket transformed the way Britain shops  ↑

[33] Office for National Statistics (2022) Tracking the price of the lowest-cost grocery items, UK, experimental analysis: April 2021 to September 2022  ↑

[34] Pandas - Python Data Analysis Library  ↑

[35] SciPy - Fundamental algorithms for scientific computing in Python  ↑

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