New Delhi, March 13 -- STOCKMARKETS ARE, in a literal sense, fortune-tellers: their job is to foresee which businesses will make money in the future and which won't. When things are not changing much, this is a matter of simple extrapolation. When change happens, it gets harder. This is obviously true in times of acute change, such as the fog of war currently enveloping the world. Yet it is also true of slower-moving but more profound disruption, like that being wrought by artificial intelligence.

Confusion over AI is everywhere. Goldman Sachs has created a share-price index of firms at most risk of disruption (see chart 1). Over the past year this has fallen by more than 20%. The bank's mirror index of "long-term AI beneficiaries", whos...