“Insurance companies have been offering hybrid indices on indexed annuities since 2012,” said Sheryl Moore, president and CEO of consulting firm Moore Market Intelligence. “Low interest rates and a challenging pricing environment have only fueled allocations to these indexes, which make the potential for earnings on these products appear more attractive.”

Sales of those products reached about $6.5 billion for the third quarter of 2019, up from just over $3 billion in the third quarter of 2015, according to data from research firm Wink Inc. And as of the end of 2018, sales represented more than a third of all indexed annuity purchases.