President Donald Trump prepares to sign a confirmation for Homeland Security Secretary James Kelly, in the Oval Office at the White House in Washington, D.C. on January 20, 2017.
CNN  — 

President Donald Trump signed an executive action on Monday that implemented a hiring freeze for some federal workers in an effort to cut government payrolls, but questions remain on whether this sort of action will actually work.

The move, which had long been promised by the Trump administration, does not include military employees, a fact Trump made clear during the signing. But research shows that federal hiring freezes regularly hurt veterans more than other groups and cost the government more because they lead to boosts in contracting.

“This memorandum counters the dramatic expansion of the federal workforce in recent years,” Sean Spicer, Trump’s press secretary, said Monday. “In particular, it prevents filling vacant positions and creating new positions except when necessary to meet national or public security responsibilities.”

He added: “It does not apply to military personnel, and it ensures that the American taxpayers get effective and efficient government.”

In an effort to counter what other hiring freezes have found, the action says it prevent the hiring of federal contractors: “Contracting outside the Government to circumvent the intent of this memorandum shall not be permitted.”

A 1982 Government Accountability Office report on hiring freezes found, though, that hiring freezes implemented by Presidents Ronald Reagan and Jimmy Carter “had little effect on Federal employment levels.”

“Because they ignored individual agencies’ missions, workload, and staffing requirements, these freezes disrupted agency operations, and in some cases, increased costs to the Government,” the report reads.

And while Trump’s executive action makes good on a promise the Republican made on the campaign trail, his press secretary’s claim that there has been a “dramatic expansion of the federal workforce” is inaccurate.

Total executive branch federal government employment – not including uniformed military personnel and legislative and judicial branch personnel – has dropped dramatically since the high point in the late 1980s and early 1990s when it averaged about 3 million employees. In recent years (such as 2009-2014) it has continued to decrease, at a slower rate, from 2.77 in 2009 to 2.66 in 2014.

The American Federation of Government Employees, the primary union that represented federal employees, blasted the announcement.

“President Trump’s action will disrupt government programs and services that benefit everyone and actually increase taxpayer costs by forcing agencies to hire more expensive contractors to do work that civilian government employees are already doing for far less,” J. David Cox Sr., the group’s president, said in a statement.

There are also concerns that a hiring freeze will adversely impact veterans, many of whom leave service and hope to land federal government jobs.

A 2015 report by the Office of Personnel Management, found that veterans made up 44% of all full-time hires the federal government.

This story has been updated.