Affluent investors are becoming more polyamorous in their dealings with financial services firms.

Fifty-five percent of investors with $500,000 or more in investable assets worked with three or more firms in 2014, said a study by Hearts & Wallets, following a behavior the financial research platform refers to as “stable two-timing,” where consumers balance a self-service firm with a full-service firm. That total is up from 49 percent the year before.

Affluent Americans are now not only diversifying their portfolios, they are also diversifying their brokers, with one-in-three households with greater than $100,000 in investable assets adding a new financial services firm relationship in 2014.

The study, "Market Measures: Reach, Share & Other 'Store' Success Measures," surprised researchers when it showed that self-service brokerage firms are popular with the affluent set, reaching 70 percent of households with at least $500,000 in investable assets, compared with just over 40 percent for full-service firms.

“It’s astonishing the self-service competitive set has deeper reach into investors with $500,000-plus, engaging more affluent investors than the full-service competitive set. Asset managers should pay attention to the self-service model,” said Laura Varas, Hearts & Wallets partner and co-founder. “Just as in retail stores, wealthy customers may trust and frequent a Bloomingdale’s, but they will still shop at Costco, too. Smart consumers compare.”

Hearts and Wallets suggests the behavior may be driven by consumers who want to use different web tools or online capabilities, or who want to obtain different advice perspectives.

The study found that Fidelity leads financial services firms with nearly 11 percent of the market share of assets held by investors with $5 million and less. That puts Fidelity nearly five percentage points above its nearest competitor, Bank of America, which has 6.3 percent of the market share.

Hearts & Wallets LLC is a partnership between two research experts in retirement market trends for the financial services industry, Chris L. Brown and Laura Varas.