As it is with individuals, so it is with companies, governments, and nations. Some thrive; others merely bump along. A few will even spectacularly crash and burn. The possible causes of these divergent life trajectories are endlessly fascinating—and not just to historians, investors, and readers of celebrity magazines.

The fortunes of healthcare practices seem to wax and wane as well. You’d like to think that unfolding scientific evidence was the main explanation for this fluctuation. But even a cursory glance at a topic in the news of late—planned home births—doesn’t support such a simple correspondence. In fact, it hardly supports any correspondence at all.

Since the second world war numbers of planned home births have fallen precipitously in the developed world, mostly to rates of less than 5% of all births. Yet over that time no compelling evidence has emerged that hospital delivery—the main alternative—routinely produces better outcomes in uncomplicated pregnancies. That has not stopped the issue becoming highly contentious, with official bodies lining up on opposite sides of the argument. For example, the United Kingdom’s Royal College of Obstetricians and Gynaecologists and the Royal College …