Washington’s largest advocacy firms are bringing in less lobbying revenue than they did in 2012, as a slowdown in the business of influencing legislation reaches its third year.

Revenue at the region’s 10 most lucrative firms fell a collective 3 percent from $173.6 million to $168.3 million in the first nine months of 2013 compared to the same period last year, according to quarterly Lobbying Disclosure Act reports filed by the firms this week. The dip follows a similar declined at this point during 2012 and 2011.

Not every firm saw a drop. Eight of the firms saw declines between 1 and 14 percent; two firms posted gains of 8 and 10 percent.

As Congress in the last two years has become increasingly distracted by debt ceiling debates and, most recently, the government shutdown, lobbyists have been moving their attention away from influencing legislation before Congress to shaping regulations put out by federal agencies. Because firms do not have to publicly disclose earnings from the latter the same way they are required to report the former, quarterly lobbying figures are a limited snapshot of firms’ overall revenue from public policy work.

“We’re continuing to see a shift in workload from LDA-reportable activity to regulatory activity that doesn’t show up in these,” said Kevin O’Neill, deputy chair of Patton Boggs’ public policy group. “We’re busy and productive in areas like financial services and healthcare, where you’ve got the regulatory cycle working on Dodd Frank and the Affordable Care Act. Those are places where over the last couple years we’ve shifted our resources. That offsets the declines in LDA revenue.”

Patton Boggs posted the biggest loss in publicly disclosed lobbying revenue among the top firms, both in lobbying revenue compared to 2012, which fell 14 percent, and in quarter-over-quarter revenue — which fell 12 percent. Some of the quarterly losses appear to be linked to top lobbyist Jon Yarowsky leaving the firm to join to WilmerHale this summer. Five clients ended retainers with Patton Boggs in July and subsequently started new ones at WilmerHale, according to lobbying records filed with the Senate. Those clients paid Patton Boggs a collective $200,000 in lobbying fees during the second quarter.

Brownstein Hyatt was one of only three of the 10 big firms that posted quarter-over-quarter gains (up nearly 17 percent). Al Mottur, who leads the firm’s lobbying practice, said that came from investing in two key areas that are poised to grow: the energy and natural resources group and the group overseeing work related to EB-5 visas, which deliver green cards to foreign nationals who make sizeable investments in certain American businesses.

“This is a competitive marketplace,” Mottur said. “Every year it’s more so. You have commoditized lobbying contracts being put out for competition with 15 to 20 firms. You have to distinguish yourself.”

Here’s how the top 10 firms fared during the first nine months of 2013, compared to the same period last year:

• Patton Boggs: down 14 percent from $35.2 million to $30.7 million

• Akin Gump: up 8 percent from $23.3 million to $25.1 million

• Podesta Group: down 1 percent from $20.6 million to $20.5 million

• Brownstein Hyatt Farber Schreck: down 1 percent from $17.1 million to $16.9 million

• Van Scoyoc Associates: down 6 percent from $16.4 million to $15.4 million

• Holland & Knight: down 1 percent from $13.6 million to $13.5 million

• Williams & Jensen: down 4 percent from $13.6 million to $13.1 million

• K&L Gates: down 8 percent from $13.5 million to $12.4 million

• BGR Group: up 10 percent from $10.1 million to $11.1 million

• Alston & Bird: down 6 percent from $10.2 million to $9.6 million