New Delhi, May 13 -- What do the Indonesian stockmarket, South Korean government bonds and Robinhood, an online broker, have in common? Not much, you might think. But over the past year investors in all three have quivered before the same phenomenon: the awesome power of financial indices.

The largest of these now exert a tidal pull on markets. As of 2025, around $36trn-worth of capital was in passive investment funds. These automatically track decisions made by MSCI, FTSE Russell, S&P Global and the like on which assets to buy and in what quantities. Many trillions more are supposedly invested actively, but by "closet index-huggers"-timid managers who fear straying too far from their benchmarks.

Ironically, all this has given rise to a...