Many of the nation’s largest lobby firms saw a spike in revenue in 2015, driven by a more productive Congress and the continuing battles over environmental regulations, trade policy, taxes and health care.

Seven of the 10 biggest lobby shops by revenue reported year-over-year gains in fees, according to year-end disclosure reports filed with the Senate on Wednesday.

Here is how the top 10 firms fared in 2015:

  • Akin Gump: up 11 percent to $39.4 million
  • Brownstein Hyatt: up 9 percent to $25.7 million
  • Squire Patton Boggs: down 22 percent to $25 million
  • Podesta Group: down 8 percent to $23.2 million
  • Van Scoyoc Associates: up 0.3 percent to $21.9
  • Holland & Knight: up 1 percent to $19.9 million
  • K&L Gates: up 4 percent to $18.1 million
  • BGR Group: up 11 percent to $17.6 million
  • Capitol Counsel: down 6 percent to $17.1 million
  • Williams & Jensen: up 1 percent to $16.9 million

“With Congress and the administration being more active, we had a good year helping our clients achieve their policy objectives through legislation and regulations,” said Darrell Conner, co-chair of the policy practice at K&L Gates. “There is a perception that [Congress] is doing nothing, and the reality is they’re actually achieving a lot.”

In 2015, lawmakers approved a number of major bills that drew intense lobbying, including from the health, business and energy sectors. Not surprisingly, lobby shops boosted their bottom line in those areas.

Congress passed “doc fix” legislation regarding Medicare payments to doctors, Trade Promotion Authority giving the White House enhanced negotiating powers on the Trans-Pacific Partnership trade agreement, an omnibus spending bill funding the government through September 2016 and a deal extending tax breaks for businesses and individuals.

It also enacted a multi-year highway bill for the first time in a decade and repealed the longtime ban on crude oil exports. Moreover, continued efforts by Republicans to roll back environmental regulations issued by the Obama administration also drove business to lobby firms in 2015.

“The administration has been aggressive on climate change and environmental issues,” Conner said. “That has led to increased regulatory work and increased legislative activity as Congress starts to push back on the administration’s climate change proposals.”

While presidential election years often mark a slowdown in business for K Street, some veteran lobbyists say 2016 may be an exception. They point to two reasons: House Speaker Paul Ryan’s pledge to restore “regular order” and some uncertainty over who will be the nominees for president.

“We’re in a period of more regular order, which we expect to continue, and that leads to regular business,” said Don Pongrace, head of Akin Gump’s public law and policy group. “Whether or not bills pass isn’t always the question. If there’s the prospect they might pass, our clients are taking notice.”

New leadership in Congress may break its election year pattern of legislating only until mid-year.

“We have a policy-oriented leader in the House in particular,” said Marc Lampkin, head of Brownstein Hyatt’s lobbying practice. “Ryan’s interest in developing a positive agenda will fill the void while the presidential campaign figures itself out. There is some optimism that the work of Congress will continue to grind on longer than perhaps in other presidential years.”