There is no official head of the U.S. National Highway Traffic Safety Administration, or of its legal, financial, and enforcement divisions. There are other vacant top posts in the Departments of Defense, State, Energy, and Agriculture, as well as the National Park Service, the National Oceanic and Atmospheric Administration, the White House Office of National Drug Control Policy, and many others. In many cases this prevents the agencies from performing at least some of their legally required duties.
What makes the situation increasingly urgent is that while there have been acting heads filling the jobs on a temporary basis, the law limits their authority to 300 days, a point that's already passed. This situation is unprecedented. No previous president has ever left so many appointed positions empty a year into his presidency.
Of 630 key jobs filled by presidential appointment -- agency heads and the second- and third-level managers -- Trump is yet to nominate anyone to fill 240 of them. Another 140 have nominees but the Republican-controlled Senate has still not confirmed them. A few of those are being held up by Democratic opposition, but most are not. In total, over 60 percent of the key jobs remain unfilled. (And this isn't counting the high-level jobs filled by people who are clearly unqualified, including the heads of the departments of Education and Housing and Urban Development.)
Worse, there are plenty of lower-level jobs that are vacant or performed by less-experienced people. More than 700,000 federal employees retired or quit during the first six months of the Trump administration alone. That's over 40 percent more than left during the corresponding period of Obama's presidency.
Contrary to popular myth, the federal bureaucracy is not overstaffed. In fact, there are about the same number of federal workers now as during the Eisenhower administration, despite expanded responsibilities and the larger population. A lot of the work today is outsourced to contractors, which (contrary to what one might think) costs a lot more than simply hiring someone in a civil service position.
Here's a brief January 29 report on the problem from PBS NewsHour:
Reporter Lisa Desjardins ends by saying charitably that we don't know whether the loss of staff at the top and in the rank and file will cause serious problems or make government more efficient. In fact, it's pretty clear that it's creating problems.