At the start of John Maynard Keynes’s obituary of Alfred Marshall comes a question: why is it so hard to be a good economist? Keynes’s answer was that “the master-economist must possess a rare combination of gifts?.?.?.?no part of man’s nature or his institutions must lie entirely outside his regard.”

This week the profession is mourning another great economist. Alan Krueger killed himself last weekend at the age of 58. What would be a bewildering blow under any circumstances is heavier still because the professor was an authority on happiness and pain.

He discovered, for example, that prime-age men who had quit the labour force were twice as likely as employed men to take painkillers. He studied how unemployed people spend their hours, and showed that actively searching for work was an intensely sad task.