Edward Newberry, a partner in Patton Boggs’ public policy and lobbying division, had an enviable book of business in 2011, based on his federal disclosure reports.

The next year, Newberry vanished — at least from the public records used to track K Street. He hasn’t appeared on any client reports filed under the Lobbying Disclosure Act since then.

But Newberry still works at Patton Boggs, the city’s largest lobbying practice. He became the firm’s managing partner, and now, instead of traipsing up to the Hill on behalf of clients, he says he delegates those duties to others so he can run the business.

Some advocates may de-register or become inactive to shield their clients or themselves from the stigma of being represented by registered lobbyists. Still others may have their eyes on a job in the Obama administration, which prohibits recently registered lobbyists from serving without a waiver. But Newberry illustrates how decisions to stop reporting federal lobbying can be driven by more mundane reasons.

“I really don’t do any lobbying now,” Newberry said. “This is a $320 million partnership, and I spend my full time in that role.”

In 2011, his clients included the cities of Greenville, S.C., and San Diego, Calif.; Inova Health Systems; Ohio University; and the Denver Regional Transportation District. He said most remain connected with Patton Boggs but are now represented by the firm’s other registered lobbyists. “We always served them with a team, and the team’s still here servicing those clients,” he said.

The Center for Responsive Politics in a recent report looked at individuals who were registered lobbyists in 2011 but who did not report any lobbying activity under the LDA in 2012 or 2013. The organization, which tracks lobbying and campaign finance data, concluded that nearly half of those inactive lobbyists continued to work for their same employers.

Experts on the LDA say the law provides many “loopholes” for those who lobby to escape reporting. Advocates who restrict lobbying activity to less than 20 percent of their time don’t need to report, and neither do behind-the-scenes advisers, unless they make more than one lobbying contact with a government official.

“I don’t think most people go out of their way to hide in the shadows, but that’s the effect,” said Tim LaPira, a political science professor at James Madison University, who focuses on lobbying laws. “I think Congress is to blame, not K Street. This is a poorly written law.”

Like Newberry, a team of lobbyists from AARP stopped appearing on the senior group’s LDA reports in 2012 but are still employed there, including Katie Gallehugh, Adam Goldberg, Fred Griesbach, Desiree Hung and Lori Parham.

Joshua Rosenblum, a spokesman for AARP, said that some of the people had taken on new roles or simply weren’t doing the requisite amount of lobbying activity to appear on a disclosure form. During the debate on the 2010 health care overhaul, he added, “we had more hands on deck” when it came to congressional lobbying.

“AARP, like many organizations, will make adjustments from time to time to meet the needs of our members,” Rosenblum said in an email.

Another ex-lobbyist who explained his inactivity in recent years was Gaston Cantens, vice president of corporate relations for Florida Crystals.

“My role is really more state issues. I’m in Tallahassee now,” he said in a phone interview. Previously, he had done some D.C. lobbying, but the sugar company has a Washington office and those employees handle Congress, he said. “We kind of just left the registration out there for a while, but I wasn’t traveling up to D.C., so we figured just to deregister.”

Justin Worrell, assistant director of government affairs at the Assisted Living Federation of America, said he “never really met that threshold” of spending 20 percent of his time on lobbying activities, which is why he dropped off the rolls in 2012. He said lobbying is a noble profession of many “good, altruistic, soulful people who believe in a cause and want to advance it.”

He later called back to say that he did not officially deregister but wasn’t sure why he didn’t appear on the ALFA’s 2012 reports and hasn’t called back since.

Chalk it up to a K Street mystery. It wouldn’t be the only one.

Other formerly registered lobbyists never did return calls to explain why they no longer appear on client LDA reports — such as Barbara Arnwine, president and executive director of the Lawyers’ Committee for Civil Rights Under Law, or Scott Packard of Packard Government Affairs.

“More and more people on K Street are realizing that gee, maybe for the most part what it is they’re doing on a daily basis doesn’t meet this strict statutory definition of the law,” LaPira said, offering one explanation for the decline in registered lobbyists in recent years.

Plus, even for those who ought to be registered, there’s almost no enforcement.

“I can’t tell you what we don’t see,” LaPira added.