A few weeks ago, the lazier end of the UK newspaper market published “research” into the tell-tale signs of a mid-life crisis, which apparently include anything from taking vitamins to looking up old flames on Facebook. The FT's science editor, Clive Cookson, somehow neglected to report the story, perhaps because it was a predictable confection scraped together by a publicity-hungry hair restoration clinic.

I have paid more attention than usual to mid-life research of late: after a long and happy partnership, this week my thirties and I will wave each other goodbye. I haven't been taking vitamins, and I won't be drawn on the subject of Facebook. But I am curious about the mid-life crisis because, PR-driven nonsense notwithstanding, intriguing research is emerging around a topic often treated as a joke.

Economists who study happiness - or, to give it its academically preferred name, “subjective well-being” - have long been aware of a U-shaped pattern as people pass through different ages. We are, on average, happier in our teens and in early adulthood, and as pensioners, than we are in middle age.