One of the more telling mistakes that Donald Trump is making is he’s entering into a period of potential economic instability with a vacancy in a position that could help him. The last chairman of the Council of Economic Advisers, Kevin Hassett, told the president in late May that he was leaving; Trump announced it on June 2; Hassett’s last day was June 28. Since then, Tomas Philipson has been the acting chairman. So it’s been almost three months since Trump learned of Hassett’s departure, and he has yet to nominate a replacement.

(In typical Trump fashion, he claimed on June 2 that he would announce a new chairman “as soon as I get back to the U.S.” from the overseas trip he was on at the time. Normal presidents try to avoid making specious promises because they care about their reputation for honesty and for following through on their plans — but not Trump.)

The Council of Economic Advisers vacancy isn’t the most significant of the 145 openings in important positions without nominees; that would probably be secretary of homeland security (Kirstjen Nielsen resigned on April 7 and her last day was April 10, so that’s over four months without a nominee for that one). But it’s an interesting one because of what it says about Trump’s approach to the presidency. For that, it’s worth going into a bit of explanation.

When the government expanded in the 1930s and 1940s, Franklin Roosevelt and then Harry Truman discovered that they were at a disadvantage in managing the newly enlarged executive branch. More agencies, and more responsibilities for those agencies, meant it was harder for presidents to affect what was happening. In part that’s because executive branch departments and agencies are as much creatures of Congress as they are of the president; Congress gives them statutory authority and sets their budgets, and the Senate confirms the president’s nominees. In part it’s because large agencies wind up with large bureaucracies that resist any kind of outside control.