The Community Food Bank in Tucson, AZ, operates its own grocery store, the Value Foods Store (VFS), which sells food items at a substantial discount from regular grocery stores. The Food Bank also operates mobile markets in Pima County, AZ, that provide items from the VFS to low-income areas with less access to grocery stores. This study uses market basket analysis to first assess the costs and availability of basic food items at local stores as well as the costs and availability of healthier versions of those items. Healthier versions may have lower fat, sodium, or sugar or higher dietary fiber. Next, market basket analysis was used to assess the impacts of mobile markets on the availability and affordability of food on the outskirts of Tucson. The two communities examined in this study were the Old Nogales Highway Colonia and the New Pascua Yaqui Pueblo, 13 and 15 miles south of downtown Tucson.
First, in-person interviews of mobile market patrons at the study sites were conducted. Basic information was collected about patron food shopping behavior and changes in behavior in response to mobile market participation. Interviews were carried out in either English or Spanish. From these interviews, a list of the grocery stores where mobile market patrons regularly shopped was obtained. These stores were surveyed to calculate the cost of purchasing the Thrifty Food Plan (TFP). The TFP is a market basket of items designed to meet basic nutritional requirements at minimal cost. The cost of purchasing the TFP (based on 1999 market basket revisions) was compared with a “healthier” basket, the items of which were lower in sodium, sugar, and fat and higher in dietary fiber than the TFP.
Prices of items in both market baskets were collected for mobile markets as well. Stores and mobile markets were surveyed in the same week to account for seasonal volatility in food prices. The costs of the two base market baskets (TFP and healthier) were calculated first. Next, mobile market prices were substituted into the two market baskets for items that were (1) available at the mobile market in that week and (2) at a lower price than at the comparison stores. This measures the maximum potential reduction in the cost of the market basket through substituting mobile market purchases for regular store purchases.
Many items sold at the mobile markets were not part of either the TFP or the healthier basket. Therefore, actual community cost savings differ from changes in market basket costs. To account for this, analysis was reversed. First, data on the number of items and their purchase prices were collected at the mobile markets. Next, local food stores were surveyed to estimate the cost if items purchased at the mobile markets were instead purchased at local grocery stores. This approach allows one to calculate total community cost savings per mobile market visit.
One-third of mobile market patrons responding to surveys reported that mobile market participation reduced their total number of shopping trips. Respondent travel time to mobile markets was less than to grocery stores, which suggests that reduced spending on gasoline is a modest benefit of mobile market participation. Based on previous discussions with nutrition educators in Tucson, there was uncertainty about whether lower income households used store discount cards. All respondents were found to use such cards at stores that offered them. Also, among respondents, there was more strong agreement that mobile market participation lowered their food costs than changed their dietary behavior. Fifteen percent of respondents purchased milk at least once per week at a convenience store, while 11 percent purchased bread and 6 percent purchased orange juice at least once per week at convenience stores.
For stores in the survey area, the healthier basket cost 12 percent more than the TFP. Based on nonparametric tests, the difference in the costs of the two baskets was statistically significant at the 0.1 percent level even with a small sample size. Whole grain products and low-fat cheeses were items most likely to be missing in surveyed stores. By substituting mobile market purchases for regular supermarket purchases, a family of four could reduce the cost of purchasing the TFP by 11 percent and the cost of the healthier basket by 8 percent. Again, using nonparametric tests to account for small sample size, the cost reductions were statistically significant at the 0.1 percent level.
Looking at actual purchases rather than hypothetical market baskets, the price discounts are larger. Results suggest that if items purchased at the Pascua Yaqui mobile market were purchased at local grocery stores, they would have cost 47-85 percent more. On average, the community saved 61 cents for every dollar spent at the mobile markets.
The absolute dollar gains to mobile market participation are limited by low total sales volumes, however. Total sales per mobile market visit are typically less than $160. Total cost savings to the community ranged from $54-$99 per mobile market visit. Direct wage costs of mobile markets were roughly $135 per visit. Other expenses (materials, gasoline) would add to costs per visit. These are primarily costs per visit rather than costs per item sold, so the cost effectiveness of the program could be greatly improved by increasing per visit sales volumes.
Direct inquiries about this study to the Project Contact listed above.