Robo-advice is boosting registered investment advisors’ client rosters, according to an annual report by the Investment Adviser Association and National Regulatory Services.

Advisors are now serving more than 36.4 million clients a 22.4% increase over 2015 – with the increase primarily attributable to the rise of automated advice for retirement plan participants and the popularity of web-based and app-based savings and investment models, says the IAA/NRS Evolution/Revolution report.

The annual report scoured data in the Forms ADV filed by advisors registered with the Securities and Exchange Commission, with this year’s report including data from 11,847 RIAs, 374 more advisors (or 3.3% more) than last year’s report.

“The trend toward automated advice for retirement plan participants, and the growth in new and existing ‘robo-platforms’ and other web- and app-based investing tools, are major themes in this year’s report,” noted Karen Barr, IAA’s president and CEO.

John Gebauer, president of NRS, added that much of the increase in the number of clients served is due to “an increase in the number of retirement plan accounts and their participants, apparently attracted by advisors offering web-based and app-based investment tools.”

The rise of automated advice, he continued, “was well timed to correspond with the retirement savings plans of a generation comfortable with technology and technology based investment tools. Investors are increasingly relying on these automated services and it is likely that technology will continue to play a vital role in the financial industry.”

The report also found that while the largest firms manage more than half the assets, smaller firms are growing at a quicker pace.

The 121 firms with AUM over $100 billion manage 53.7% of the total industry AUM, but for the first time in recent history there are fewer of them (down from 128 firms in 2015), with less in AUM (down 2% from 2015).

By contrast, the 8,565 firms (72.3%) with AUM under $1 billion manage just 3.4% of total industry AUM, but their AUM was up by 2.5% in 2016. Firms with AUM between $1 billion and $100 billion saw their AUM grow by 3.1%, the report states.

The majority of advisors continues to be small businesses, with 87.8% (10,404) of advisors reporting employing 50 or fewer nonclerical individuals – while 56.8% (6,725) report having 10 or fewer nonclerical employees. Industrywide, the median number of employees is nine, the report found.

Most RIAs also focus their services on one category of client, with more than 87% reporting that the majority of their clients come from a single category. For instance, nearly 51% of advisors report that more than half of their clients are individuals, while another 29% say that most of their clients are pooled vehicles (registered or unregistered).

Many of these advisors serve pools exclusively: 2,093 report that 100% of their clients are private funds, while 301 advisors report that 100% of their clients are registered funds. More than 7% specialize in non-pooled institutional clients.