P92 Controlling for Confounding Factors in a Multi-Component Farmers’ Market Intervention


      Despite federal funding to encourage SNAP EBT use at farmers’ markets, only $22 million or 0.03% of the $70 billion total SNAP dollars are spent in these direct-to-consumer channels.


      The objective of this study was to determine if confounding factors such as weather or other market activities have an impact on SNAP sales compared to typical market days.

      Study Design, Setting, Participants

      This 4-year, quasi-experimental study used a multi-component intervention at a medium-sized, weekday, year-round farmers’ market in northern California. Total SNAP sales were collected over 54 baseline and 136 intervention market days, respectively. SNAP recipients were the target population, however several intervention components were available to all market shoppers. The multi-component intervention included SNAP outreach (ie, on-site eligibility screening, SNAP application assistance, and SNAP material distribution), SNAP signage, financial incentives (ie, Market Match), and nutrition education including food tastings highlighting market produce, recipe cards, posters, and market education.

      Measurable Outcome/Analysis

      The primary outcome measure was SNAP sales. Data about potentially confounding factors including bad weather (ie, rain, heat advisory conditions, and poor air quality) and unusual circumstances (ie, school field trips, WIC distribution days, federal holidays, and issues with the intervention programming) were also collected for each market day. Mann-Whitney tests were run for the baseline and intervention periods separately to assess if these factors had an impact on sales.


      During the baseline period, SNAP sales were significantly lower on the 9 market days that experienced bad weather (P = .01). However, bad weather did not have a significant impact on SNAP sales during the intervention period. Unusual circumstances did not have a significant impact on SNAP sales during the baseline or intervention periods.


      In order to determine which market days to include in subsequent SNAP sales analyses, confounding factors should be investigated.
      Funding USDA, California Department of Food and Agriculture and Ecology Center.

      Appendix. Supplementary data