Why do people waste food?

The author and celebrity chef Dan Barber had an op-ed yesterday in the New York Times that touched on food waste.  Oddly, he seems to associate waste with large-scale specialized agricultural grain operations.  In fact, these are the crops that are most easily stored and transported, and it is these larger farms that have easier access to storage facilities and technologies to prevent waste.  

In any event, I'd say Barber's editorial is fairly representative of the larger literature on food waste.  That is to say, food waste is seen as something akin to a "sin" or to a "mistake" that we must stop at any cost.  Take for example, this quote from a National Geographic article:

Ethically, food waste is bad.

I suspect most economists have a hard time with this sort of reasoning.  The decision to discard food is a decision like any other economic decision.  Deciding to discarding food is "bad" only to the extent that there is some sort of market failure.  To be sure, there may be some un-priced externalities associated with waste, but these aren't often well articulated by advocates of food waste reduction.  Even still, it isn't the decision to discard that is "bad", what is "bad" is the lack of a market to price the externality.

A useful starting point is to go back to first principles and understand the economic factors that "reasonably" or "rationally" lead people to discard food in the first place.  That is precisely what Brenna Ellison and I have tried to do in a new short paper that was just published in the journal Applied Economics Letters.

The paper constructs a mathematical model of consumer behavior based on the notion that people take prices and wage rates as given and then choose how much time to spend working, how much time to spend in food preparation, and how many raw food ingredients to buy so as to maximize their well-being (which is defined by the meals they eat and the amount of time in leisure).  In this so-called household production model, consumers are also producers: they combine their time with raw food inputs to produce meals, which are the ultimate source of value for the consumer.

It is actually hard to conceptualize "waste" in a model like this (or any economic models of optimization).  I've heard heated debates between some of my fellow agricultural economists over this matter, and there is a camp that would argue (quite persuasively I might add) that there is no such thing as waste.  In that view "waste" really would represent a mistake or an arbitrage opportunity.  If someone valued my trash more than I did, they ought to be willing to pay to take it from me; if no one does, then (as I actually do) I pay someone else to remove it, who finds no other economical use for it other than to bury it and let nature take its course.  In this more strident view, we might "discard" items, but a well functioning economy doesn't "waste" items.  

All that is to say, in a mathematical model like ours, one has to have some way of defining waste.  We define it as the the inverse of the amount of meals produced per unit of raw food input.  A cynic might say: you've just redefined the marginal productivity as raw food inputs as waste.  Guilty as charged.  If you have a better solution, I'm happy to hear it.  

In any event, this set-up allows us to view waste as a function of economic variables.  We show that:     

Differences in market prices for raw food ingredients, p, or differences across food
consumers in the opportunity cost of their time, w, might thus explain differences in food waste. It is also possible that education, background, or cooking ability can lead to different marginal productivities of time used in meal preparation.

The nice thing about this approach is that one can also assume that people combine their time and food inputs to produce other things (in addition to meals) like human capital or health.  If so, it is also possible to show that if consumption of a meal lowers health (e.g. by consuming a spoiled or raw ingredient), a larger amount of waste might be optimal.

If one is willing to accept some assumptions about the mathematical relationships involved, the model produces some testable hypotheses.  Namely:

  • individuals with higher wages will have more food waste,
  • individuals with higher non-wage income will have less food waste,
  • individuals with greater talents/ability/education at turning raw food inputs
    and time into meals will waste less,
  • the amount of waste will depend on the extent to which people prefer leisure to meals.

Importantly, in this framework waste is not a "mistake" nor is it "unethical" - it is the best thing for the consumer to do given their income, prices, and preferences.  For waste to be a "bad", my decision to discard food would have to affect other people not involved in my decision.  One could imagine situations like this and this sort of frameworks provides a starting point for thinking about costs and benefits of policies and initiatives aimed at reducing waste.

I'll conclude by noting that even the Onion knows there are "rational" reasons to discard food that aren't "bad" or "unethical".  Here are few of their humorous suggestions to cut down on food waste.

Avoid impulse buying by only going to the grocery store for one ingredient at a time.

Hire an impoverished family to sit at your dinner table and guilt you into eating every last morsel.

Make sure to eat the oldest items in your fridge first, as listeria will deter you from additional grocery purchases for the next seven to 10 days.

Instead of buying a whole tub of strawberries and an entirely new can of whipped cream, use the remaining half can of tomato paste, last serving of chicken piccata, or whatever other leftovers you have in the fridge to spice up your love life.

Try not to prepare more food than you can eat, unless you are entertaining the Lady Carroway for supper and must impress her with your bounty.

Make use of expired food by reaching out to any neighborhood kids who can be dared to eat it for a few bucks.