Rep. Michael Capuano pays his employees very well.

In fact, the 10-term Somerville Democrat has the highest average staff salary of any lawmaker in the United States Congress, either House or Senate. The mid-range salary in Capuano’s office was $81,000 last year, according to a website called that tracks congressional spending records.

The mid-range for all congressional staff was about $51,000.

By contrast, Rep. Seth Mouton, a Democrat from Salem, had a mid-point staff salary of just over $41,000 last year, one of the 20 lowest average salaries in Congress. That’s because Moulton, only on his second term, has more young, lower-paid staff in his office than Capuano. Moulton’s average will likely rise this year because he recently hired a new chief of staff earning more than $100,000.

Capuano’s staff members also got generous year-end bonuses. Capuano distributed about $124,000 in year-end bonuses to his staff, more than double what he gave out at the end of 2016 — with 10 employees getting bonuses of $8,300 and one getting $12,500. Nobody else in the House gave out more in year-end bonuses last year, and only three other lawmakers topped $100,000 in year-end payouts.

Median salary of staffers, Massachusetts delegation to congress
WGBH News/Data courtesy of Legistorm

An individual member of Congress has limited ability to shape any legislation or public policy debate, but the office budget “is one of the few things that lawmakers can do all by themselves to make some kind of statement about fiscal responsibility or constituent service if they feel that way,” said Pete Sepp, President of the National Taxpayers Union, a Washington non-profit that advocates for low taxes and limited government. “There are some lawmakers who take pride in being very parsimonious with their [office accounts] . . . returning that money to taxpayers.”

But Sepp notes, “Other lawmakers might believe that spending a lot of the allowance is an important indication to show their constituents that they believe in delivering the best possible service to them.”

Casey Burgat, a fellow at a DC-based think tank called R Street who is studying congressional staff for his doctoral dissertation, said the expenditures from the office budget “is one of our best indicators of what is most important to the members themselves.” Burgat said staff tenure in the House is generally pretty low, but there is a correlation between staff seniority and legislative achievement. “Offices with high staff turnover introduce fewer bills and are less successful in moving them through the process,” he said.

Every House member received a taxpayer-funded office budget of about $1.3 million in 2017 to cover payroll, office travel, rent for offices in the district and supplies. Some members get a larger budget to cover excess travel costs if their districts are far from Washington, or if their district offices are in areas with high rental costs.

More junior members of Congress or those in competitive districts may be more inclined to spend on district mailings or constituent outreach, things that raise their profile and boost their re-election chances, instead of salaries, Burgat said.

None of the House members mentioned in this story were willing to discuss their budgets — not a surprise, Burgat said. “I don’t know that there are a lot of good stories that can come out of members talking about how much they spend on themselves,” he added.

Capuano spent all but about $5,000 of his budget last year; only six lawmakers had less money left over at the end of the year. Moulton had about $15,000 left over, ranking in the top 40 spenders, and Rep. Richard Neal had nearly $95,000 left over — the highest surplus of any Massachusetts member of the House. Neal’s remainder is about the average for House offices.

Capuano’s office notes that his salaries are high because he has five staff members who have worked in his office since he was first elected to Congress in 1998 and three others who have been on staff for 15 years, so their pay has increased over time. Rep. Richard Neal, who has been in congress since 1989, had a median staff salary of a little over $49,000. But as the top Democrat on the Ways & Means Committee, Neal also has staff on the committee’s payroll, which could be offsetting some costs that would otherwise fall on his office.

With a lower payroll, Moulton spent more of his budget on travel and website development than Capuano.

The Senate operates on a different budgeting system, but Sen. Elizabeth Warren and Sen. Ed Markey each had a budget of about $3.3 million for 2017. Warren ended the year with about $54,000 left over and Markey left about $304,000 unspent.

Markey also has a well-paid staff. His median staff salary last year was $73,000, the fourth highest number in Congress, according to Legistorm. Warren’s average staff salary was a little under $51,000.

A handful of members wear their frugality as a badge of honor. Rep. Daniel Webster, a Florida Republican, ended 2017 with more than $400,000 left over in his office budget and issued a press release about the achievement. “Washington operates on the principle that if money is appropriated, it should be spent,” Webster said. “During my service in Congress I have exposed this flawed principle.” Webster says over the seven years he has served in Congress, he has saved nearly $3 million from his office account.

How much members of Congress pay their staff — and how much they have left over in their budget to do so — varies widely from member to member. The chart below shows how much each lawmaker had leftover at the end of 2017.

New England Center for Investigative Reporting intern Lucas Smolcic Larson contributed to this report.