According to a Boston Globe review of city records, police payroll has increased by 43 percent over the past decade, with overtime growing at a higher rate, about 84 percent over the same period.

Former Secretary of Public Safety Andrea Cabral told Boston Public Radio this data shows a key difference in how police contracts are negotiated compared to other city employees.

"Boston Police, their base pay represents the lowerst percentage of what they make, which means that overtime and other make up a significantly greater portion of what they make verus fire department emplyees, Boston education employess or other City of Boston emplyees, and that's the fundamental problem," he said.

As calls for police defunding gain traction and people look to the systems that make police reform difficult, the power of police unions is coming into focus.

"These are the kinds of provisons that get built into a contract that then becomes cemented over time and they're permanent," she said. "So even when times are better and the rates of salary increase that people seek are granted, they still have these other things to fall back on."