“Overall, my reading is that the Trump political appointees have less expertise, in their respective areas, than any presidential administration dating back to at least the Reagan era,” said Thomas E. Mann, a senior fellow at the Brookings Institution who reviewed the database. Mr. Mann has specialized in federal government studies for four decades and has tracked the process that previous administrations have used to fill political jobs.

Lindsay Walters, deputy White House press secretary, said the administration had appointed well-qualified staff.

“The president selects the highest caliber of individuals from an array of backgrounds and experiences to fill positions in his administration,” she said in a statement. “We are proud that these individuals — whether they worked on the campaign, conservative think tanks or elsewhere — share the president’s vision that got him elected.”

Agency officials added that these new political hires had brought value to government. For instance, Heather Nauert, a State Department spokeswoman, said in a statement that Matthew Mowers, the former Trump campaign official who recently traveled to South Africa, provided a “fresh focus and renewed passion for helping women, children and men who are living with H.I.V./AIDS.”

Mr. Mowers, who had also worked on the presidential campaign of Chris Christie, the former governor of New Jersey, is chief of staff in the Office of the U.S. Global AIDS Coordinator. Last month, he tweeted from South Africa, “Great meeting today with Ministry of Health Officials in Johannesburg.”

One of the top sources of the appointees has been the presidential campaign, according to the database. Some of the people listed in the database have already left the Trump administration, but it offers a snapshot of those hired for political jobs in the past year. At the White House alone, there have been almost 60 former campaign workers. In addition, about 20 have been hired at the Energy Department, and another 20 or so at the Commerce Department.

Some of the Commerce jobs have been filled with people who have extensive experience in government or the private sector. One of them is Mira Ricardel, the under secretary for export administration, whose career includes stints at Boeing, at the Defense Department and on Capitol Hill. During the campaign, she was a consultant to Trump for America.