A good British nanny used to be hard to find. Mostly high-powered bankers, lawyers and big media types—fat on the '90s equities boom—could afford them. Experienced nannies commanded salaries that rose in lock step with those of their employers—roughly 25,000, or $37,000, in 2002. Then there were the perks: complimentary mobile phones, gym memberships, even free cars and overseas vacations.

Ah, those were the golden years of what Liz Roberts, editor of Nursery World magazine, calls the "nanny bubble." Alas, the halcyon era has gone.

But the latest example of such madness, according to Barton Biggs, a veteran investment guru at Morgan Stanley Dean Witter, is the nanny bubble.

Rich investment bankers with lots of children are moving into huge mansions…where they need not one, but often two live-in nannies. But there are not enough to go round. So the price of nannies in Greenwich, Connecticut, where Mr Biggs lives, has soared.

According to Barton Biggs, economist at US investment bank Morgan Stanley Dean Witter, the "nanny bubble" is the ultimate phenomenon which has hit Wall Street. Wall Street economists — Biggs says — are rich and affluent, have young good-looking wives and many children; only the "round-the-clock nannies" are able to facilitate their life-style. The business linked to nannies has indeed resulted in the creation of a status symbol: using Biggs' words, "you cannot be a real family without at least two live-in British nannies". The only problem, Biggs says, is that there are not enough nannies and therefore the baby-sitting price per hour has rocketed.