For the past year or so, I have been working on a paper with my colleague Rob King which I am hoping to debut sometime soon in which we look at the relationship between farmers markets and food-borne illness.
I have presented that paper twice so far–once at Ohio State, and once at Oklahoma State. Every time I present it, one thing that comes up is whether there is reverse causality, i.e., whether people perceive the foods they buy from farmers markets as safer than the foods they buy at supermarkets, which would lead to a spurious relationship between farmers markets and food-borne illness because increases in the number of outbreaks and cases of food-borne illness would then cause increases in the number of farmers markets.
After my talk at Oklahoma State, I was discussing this with Jayson Lusk, who had invited me to give that talk, and the outcome of our conversation was that we simply didn’t know what most people would think. So Jayson (whose blog you really should be reading if you don’t already) decided to include a question to that effect in his monthly Food Demand Survey (FooDS), and which he discussed in a post last week:
Three new ad hoc questions were added this month, two of which are discussed here.
The first question was motivated by a research seminar that Marc Bellemare from University of Minnesota presented here at OSU last month. His research suggested that an increase in the number of farmers markets in a particular location was associated with an increase in food-borne illnesses in that location. I was curious whether consumers thought farmers market food was more or less safe than grocery store food (it was also a question Marc was keen to ask). So, respondents were asked, “Compared to food from a supermarket, do you believe food from a farmers’ market is more likely or less likely to cause food borne illnesses resulting from bacterial or viral contamination?”
There was no clear consensus. About 28% or respondents thought food from a farmers’ market was more likely to cause illness than from a supermarket, about 45% thought “food from a farmers’ market is neither more or less likely to cause food borne illnesses than food from a supermarket” and 27% thought farmers’ market food was more safe than supermarket food.
Here is a histogram of the responses accompanying Jayson’s post (click on the image for a bigger version of it):
It is nice to finally have some light on this topic, and I am grateful to Jayson for asking that question, because my coauthor and I can now point to Jayson’s survey to argue that the overall effect of consumer perceptions regarding the safety of farmers market foods relative to food from other sources is unlikely to introduce reverse causality, given that the expectation appears to be zero in the above histogram.