Alan Krueger, then-chairman of the Council of Economic Advisers, at the White House in 2012. (Kevin Lamarque/Reuters)

I have had no student of whom I have been prouder than Alan Krueger. It has taken me a few days since the shock of learning of his death to think of how I wanted to pay tribute to him.

Alan was the kind of student who is the most satisfying to teach. He was not the kind of genius who grasps everything instantly, making his instructor feel unnecessary or irrelevant. Instead, he was someone with an extraordinary gift that could be unlocked through the diligent work of mastering the basic techniques of the economics field.

What made Alan perhaps the most interesting and influential labor economist of the past four decades? Although many say economics is too much applied math, it was not preternatural mathematical statistical talent. Nor was it an ability to think through hard problems at high speed.

Alan’s gift was something different — something that cannot really be taught. He had the knack of identifying important questions that he could convincingly answer with the data and data-analysis tools at his disposal. Again and again, sometimes on his own and sometimes with a range of co-authors, he shed light on the most important issues regarding labor markets. Our understanding of the economy and, equally important, how best to do economics was forever changed.

Take his celebrated work with David Card on the minimum wage. They looked at how relative hiring patterns changed when one state raised its minimum wage and one right on its border did not. Not much except the minimum wage differed between the two situations, so it was about as close to a controlled experiment as economists will ever get. Alan was a pioneer in the exploitation of such natural experiments. After Alan showed what kind of evidence can be marshaled to study a labor-market intervention, economists have raised their standard of what constitutes convincing evidence. What followed has been called a “credibility revolution” in empirical economics.

Alan’s knack seemed to include not just finding answerable important questions but sensing when the answers were likely to be new, surprising and overturning of conventional wisdom. The finding that raising the minimum wage did not reduce employment is only the most famous example. His research also has demonstrated convincingly that poverty is not a cause of terrorism, that past a certain point economic growth is good for the environment, and that even marginal increases in schooling meaningfully increase workers’ market value.

All these accomplishments could have been enough. But Alan wanted to serve more directly. And he did that with three major stints in government at the Labor Department, the Treasury Department and the White House Council of Economic Advisers. His heart and temperament were those of a professor of economics, not a political operative, but he turned that into an asset. Others in government meetings had their opinions or their agency’s position or their talking points. Alan always had a survey of the academic literature at hand, and sometimes, as in the Obama administration’s internal debate on wage subsidies, had his own specially commissioned survey to report.

It mattered. Whether in the Clinton administration’s push for higher minimum wages, the Obama administration’s emphasis on spurring hiring after the financial crash or in its focus on the problem of jobless middle-aged men, Alan was one of the rare academics in government who had a real impact on policy.

Many distinguished economists have worked in government over the years — most but not all at the Council of Economic Advisers. Alan stands out in a final respect. After he returned to academe, he did not rest on his laurels or become a commentator and consultant on all matter of economic issues. Rather, he returned to great effect to doing serious academic research on opiates, on the determinants of happiness and even on the economics of rock music. His commitment to research was an inspiration to me and many others.

Always, from the day he walked in to my office at Harvard as a first-year graduate student, Alan seemed a happy man, excited about what he was learning and teaching, intensely connected to his family, looking to his next tennis game and his next trip. He certainly enriched the lives of all those honored to count him as a friend and helped make life better for millions of people who will never know his name. Alan’s life was short, but his legacy will be long. Rest in peace, my friend.

Read more:

Catherine Rampell: Alan Krueger’s minimum wage research was remarkable. So was his happiness work.