(Bloomberg) — Buyers of U.S. annuities are clamoring for new products linked to indexes that may use elaborate strategies to control risk, attracting regulatory scrutiny as they widen a market that favors more traditional structures.

A total of 27.7 percent of indexed annuities sold in the third quarter of last year are tied to measures that track stocks and other types of assets, such as cash or commodities, according to Wink's Sales & Market Report. A year ago, these types of indexes didn't exist in Wink's market data.

Consumers last year purchased an estimated $47 billion of indexed annuities, which are structured insurance products, according to Alan Grissom, global head of insurance at S&P Dow Jones Indices, in a Jan. 22 webcast hosted by the National Association for Fixed Annuities. That would be a 21 percent jump from the $38.7 billion sold in 2013, Wink's data show.