Advisors in the U.S. keep gaining assets. But that growth could face major challenges in the future, predicts Cerulli in a new report.

For one, the Boston-based research firm found an almost across-the-board slide in advisor head count in the five years through 2013. In that period, wirehouse numbers dipped by 2.8%, slightly more than the industry average.

The only segments to show a net increase in head count were RIAs, at 1.8%, and Cerulli’s dually registered channel, at 9%. But even in these cases, researchers added a caveat, noting that “much of this expansion results from advisor movement rather than from new advisors entering the industry.”

In the short term, Cerulli sees some relief: It’s forecasting about 1% head count growth over the next few years. The report says the uptick will be due in part to a new emphasis by “employee-based firms on reinstated training programs.” At the same time, its analysts say indies are more likely to put resources into developing a cadre of junior advisors to support future revenue growth.

But while industry surveys indicate just 4% of advisors plan on leaving the profession in the next five years, FAs tell Cerulli that planned exits in the next five to 10 years could top 20% of the advisor force.

RIAs produced 14.5% five-year growth in AUM, compared with 8.4% for the wirehouses. Of course, that was off a much smaller base: Wirehouses account for 42.1% of the asset pie, the indies just 11.9%.

Another point worth mentioning is that a typical wirehouse advisor works with a much bigger book. At the end of 2013, the research piece pegged AUM for an average FA at one of the big-four brokerages at $124.7 million. By contrast, an average RIA advisor had about $58.6 million.

“While growth rates for the wirehouses have been less robust than those in the RIA space, the four massive firms continue to dominate market share,” Cerulli says. And its analysts note that, as of the latest study, wirehouse advisors remain the industry’s “most productive” force.