Stanley Karnow had it right when he said many years ago that a reporter’s toolkit consists of two main things: background knowledge and skepticism.  He might have added that a good supply of shoe leather helps as well.

I was reminded of Karnow’s maxim by the death on March 14 of Alan Krueger, 58, of Princeton University.  I was sad to think I hadn’t seen Krueger or spoken to him since 2011, when he became chairman of President Obama’s Council of Economic Advisers, succeeding Austan Goolsbee.

At first I thought the lapse must have been a function of my having left newspapering for the Web a decade earlier. Then I decided it had more to do with the life cycle. I was spending more time writing books and less time covering the beat.

My sense of loss was nothing compared to the grief expressed in the community of labor economists, which recognized that the irony that a man who had spent much of his career studying the ill-effects of reversal on others, mostly economic, had died by his own hand. Catherine Rampell, of The Washington Post, reviewed his career.

Krueger was born in 1960.  That meant he was twenty-one years old in 1981, the year IBM began running those Charlie Chaplin ads for its new “microcomputers.”  The age of highly adaptable personal computers was just getting underway.

He graduated from Cornell University’s School of Industrial and Labor Relations, in 1983, then did his graduate work at Harvard University, graduating in 1987.  Princeton University hired him and put him in the office next to Professor David Card, four years his senior.

By then, a broad movement in empirical economics was underway.  Card thinks some part of it started with Robert LaLonde’s work on the evaluation of competing methodologies. I have often heard that Joshua Angrist’s study of the effects of the Vietnam draft lottery on the lifetime earnings of draftees was especially influential. Princeton’s Orley Ashenfelter was the dissertation adviser of each, and Card as well.  Harvard professor Richard Freeman’s search for natural experiments is often mentioned.

Krueger brought with him to Princeton a subscription to the New England Journal of Medicine, each of its articles prefaced with a description of the particular”methods” and “research design” by which the result was obrained.  Card , laughing, recalled in an interview,”[It] would come in every week, so there was a lot of stuff to read…. And if you’d never seen that before, and you were educated as an economists in the 1970s or 1980s, that just didn’t make any sense.  What is rsearch design? And I remember ne time I said, ‘I don’t think my papers have a research design.’ ”

Card and Krueger contributed a widely-cited study and subsequent book about what happened in the fast food industry when New Jersey raised its minimum wage and Pennsylvania didn’t. They concluded that raising the minimum wage had relatively little impact on employment. (Their finding generated both controversy and further research.) Randomized controlled trials soon followed in development economics, and field experiments of various sorts, and, eventually, the application of machine learning to big data.

Financial Times columnist Tim Harford noted yesterday that Krueger liked to call all this “the credibility revolution.” Nobel awards haven’t begun to be awarded to economists in the movement yet, but they will.  Card was recognized with the John Bates Clark Medal in 1995 as an especially influential economist of his generation before the age of forty.

I have long thought that there is a good book to be written about the methods revolution.  That was the biggest thing going on in economics for many years after 1990. I’m not the man to do it; my shoe leather budget shrank dramatically after I left the Boston Globe. When that book is done, it will assign a prominent position to Alan Krueger.