Early in my career I had the immense good fortune to work with Garrett Hardin, a distinguished ecologist. He was an extraordinarily fine and brave gentleman and scholar. Garrett was also sufficiently honest to admit his occasional errors and modify his analysis accordingly. Together, we produced a book that remained in print for nearly 20 years, Managing the Commons. I learned a great deal in the process and want to share an important lesson.

I was teaching at Indiana University during the first Earth Day. My field was political economy with a focus on natural resource economics and ecology.

In the spirit of the time, some professors from the biological sciences became interested in environmental policy. A few of them pontificated some extraordinarily silly ideas. Nearly all of them required draconian governmental dictates often based on wildly unrealistic predictions. These folks were sincere, successful in their fields, and smart. Yet their pronouncements implied that when they strayed from biology into public policy their IQs and body temperatures suddenly converged. This puzzled and disturbed me.

I explained this to Professor Hardin and asked his advice. Given that I worked in an inherently interdisciplinary arena, I had a problem: How could I determine with whom it would be worth working and who was blinded by politically correct thinking? Here’s his answer.

Garrett suggested the following test. When someone offers a policy prescription that seems inconsistent with the way the world works, ask this question: “And then what? What are the logical consequences of his policy recommendation?” Has he considered the long-term consequences of his idea? If not, the individual confused good intentions with likely outcomes.

Garrett claimed that good ecologists just naturally asked themselves the “And then what?” question before offering a policy recommendation. He advised me that university politics aside, those who failed to do so could be ignored with impunity. (That’s when I discovered that economics can be understood as a branch of evolutionary biology, i.e., they are logically alike, intellectually isomorphic.)

Garrett was not alone in this thinking. Harvard economist Arthur Smithies offered identical advice to his student Thomas Sowell, now at Stanford’s Hoover Institution. After an “And then what?” grilling by Smithies, Sowell writes: “I was beginning to see that the economic reverberations of the policy I advocated were likely to be pretty disastrous -- and in fact, much worse that the initial situation that it was designed to improve.” And that’s why economics is the dismal science, i.e., its application separates pious hopes from prudent expectations. While politicians promise solutions, economists sensitize us to necessary trade-offs.

Let’s explore the problem of housing. We can all think of desirable goals such as affordable housing and open space. The economics of housing leads us to consider the inescapable costs of achieving such goals. It tells us that not all good things can possibly go together. If, for example, we require large lot sizes, prices per house will increase. If town apartments are limited to three stories, prices will rise. As prices increase, folks of modest means will commute from less expensive areas and traffic congestion will become worse.

We all know that there are many deserving people in our community who cannot find adequate housing that costs 30 percent of their income. Is rent control an answer? Folks who fail to ask the “And then what?” question find it attractive. If one thinks only in terms of preferred results, he sees immediate benefits while remaining blind to the incentives and constraints which naturally flow from the policy.

But if we impose rent control, shortages will follow. Demand will increase while the supply will lag and may even decrease. Quality and maintenance will slip. Black markets will emerge. Builders will go to less constrained locations and the average age of houses will increase because fewer new houses will be built. Since luxury housing is usually excluded from rent control, developers will shift toward the high-end market. Affordable housing will become even harder to obtain.

Across time and cultures, all of these unfortunate outcomes naturally follow. All are the predictable consequences of a well-intentioned policy. All could have been avoided if policy makers had asked “And then what?”