Like all good economists, I am both frugal and insensible to considerations of style, so my battered old spectacles are now more than a decade old. I’d be lost without them, quite literally. My unaided eyes are unable to read a book at a distance of more than four inches. Occasionally, this serves as a superpower – I can take my glasses off in tedious meetings and drift away, as blissfully blind as if I had pulled my jumper over my head. Usually, however, I prefer to be able to see, and so the glasses have followed me into the shower, the karate dojo, and a number of other situations that need not be detailed here. As a result, I rarely mislay my glasses – which is lucky, because they are slim enough that I find them invisible at a range of 3ft.

On the occasions when I do lose them, one thought often leaps into my mind: thank goodness I was born after eyeglasses were invented. Without them I would be severely disabled; with them perched on my nose, that description seems absurd.

The modern world is, of course, full of helpful stuff, from spectacles to penicillin to e-mail – stuff we tend to take for granted, but shouldn’t. The economist Timothy Taylor, editor of The Journal of Economic Perspectives, begins his introductory economics lectures by asking his students whether they would rather be making $70,000 a year now, or making $70,000 a year in 1900.