Insurers tend to steer clear of big equity bets. But as semiconductor stock prices rose this year, they didn't rebalance. They kept buying. That's the upshot of an analysis of client holdings by investment-management software firm Clearwater Analytics. As a result, the firm found, semiconductor stocks ticked up to a median 1.7% of insurers' equity portfolios from 1.4% in the first seven months of this year.

The book value of insurers' semiconductor stocks grew 54%, slightly more than the 50% growth in market value over that seven-month period, Clearwater found. In contrast, the book value of their energy stocks grew 14% far less than the 30% growth in market value. "It's a bet that the energy story is a one-off cyclical one that is likely to fade and the chip story is something here to stay," said Clearwater head of research Matthew Vegari.