ELON Musk, the world's richest man even with the devalued Tesla shares, has something in common with some Filipino academics of the celibate kind: they believe that the trajectory of population should be upward, in an expansionary mode, free from controls and regulation. Mr. Musk does the actual thing, the prodigious fathering, he practices what he preaches. The question now being asked is, how many kids does he actually have? He is also duly alarmed by slowing population growth, low child births, shrinking populations in the major economies.

Mr. Musk, who needs to staff his various tech-oriented enterprises, has reason to be duly alarmed. The median age in the US is around 38. And that is really old for the world's biggest economy.