Agent and broker organic revenue growth climbed to 5.1% for the first quarter, up from 4.6% for all of 2015, Atlanta-based Reagan Consulting Inc. said Tuesday, but pricing issues and a slowing economy could hit agency growth rates later this year.

The firm’s “Organic Growth and Profitability” quarterly survey report found that first-quarter profit margins were slightly lower at 28.5%, compared with 29% in the year-ago period. Median profitability, as measured by earnings before interest, taxes, depreciation and amortization, or EBITDA, was still strong by historic standards.

First-quarter profits are always inflated due to contingent income, Reagan Consulting said in a statement, but are expected to finish the year at roughly 20%, which the firm said would be another solid year.

“Given the powerful headwinds of softening commercial property and casualty pricing and continued weakness in the U.S. economy, the upward movement in growth is positive,” Kevin Stipe, Reagan Consulting’s president, said in the statement.

The employee benefits sector saw 6.9% growth, the strongest in the quarter, Reagan said, noting that growth at that pace would yield the fastest yearly rate for employee benefits since 2011. Commercial property-casualty grew at a 5.1% rate while personal lines grew at 1.6%.

Mr. Stipe said commercial rates and the sluggish growth rate are pressuring agencies.

“If pricing continues to deteriorate and the economy doesn’t pick up,” he said in the statement, “agency growth rates are likely to suffer later this year.”

The survey measures sales velocity, defined as new business written as a percentage of prior-year overall commissions and fees, which reached 12.1% during the first quarter of 2016. Sales velocity is the greatest differentiator of high-growth agencies, Mr. Stipe said, adding that firms achieving a 15% or higher sales velocity grew by 7.1%, while those that achieved less than 10% grew only 2.2%.

The survey does not measure merger-and-acquisition activity among agents and brokers, but Mr. Stipe said in the statement that it continued at a “blistering pace.” Deals topped 107 for the quarter, compared with an all-time record of 124 in the first quarter of 2015. Mr. Stipe said the outside world, driven by private equity, “has fallen in love with the investment performance of insurance brokers,” and is driving agency valuations to “levels never seen before.”

Reagan Consulting, which has conducted the survey since 2008, uses confidential submissions from about 140 midsize and large agencies and brokerage firms. Roughly half the industry’s 100 largest firms participated in the most recent survey, and median revenue of the firms completing the survey is about $17 million.