New Delhi, June 5 -- AMERICA'S SOCIAL Security trust fund for the country's elderly citizens is now more than old enough to be drawing a pension itself. When the programme launched in 1940, its future must have seemed assured. Lots of money went in and little came out: for each retired person drawing benefits, more than 150 workers were contributing to the fund, which invested in Treasury securities.

Today, after years of demographic transformation-lower birth rates bringing fewer workers to the labour force, and longer lifespans for the fortunate recipients-the ratio of workers to recipients is less than three to one. In 2017 the reserves held in the trust fund peaked at $2.8trn. Since then, the fund's size has dropped by $400bn, with m...