Now when did consumption start to take on immoral dimensions? The first obvious case was when people began noticing that some consumption produced indirect harms, e.g., pollution. These externalities are intimately linked to the consumption, so the quick way to reduce them is by reducing consumption. (A slower, more effective way is to change the production or consumption process so each “good” comes with less “bad.”)

A less obvious case is when consumption facilitates other activities that are harmful. To some people, overpopulation is one such activity. How does more consumption lead to overpopulation? By making it easier to afford kids.

Take the example of food. For most of human history, food was expensive. Kids, therefore, were also expensive. When technological development (fertilizers, seeds, machines, etc.) made it cheaper to produce food, we got two results: Those who were alive could consume the same amount of food in exchange for fewer resources, and the cost of children fell. Taken together, we can therefore see how the Green Revolution has contributed to both obesity and overpopulation — two unintended consequences that we suffer from today. (Although these consequences were predictable, they would not have stopped innovation or the Green Revolution. Although society was made worse off as a result, individuals benefitted, and individual benefits are what drive adoption decisions.)

Note that obesity and overpopulation are only “bad” in the sense that they create negative outcomes (public health costs and environmental stresses, respectively); cheap food is not bad, per se.

Bottom Line: Because our internal controls on behavior have developed over thousands of generations, we find it very difficult to change our view of something formerly “good” to something now “bad.” As a result, we are likely to behave badly — unless some external controls (prices) are imposed.