Since 1950, the average age of heads of government in the three dozen member countries of the Organization for Economic Cooperation and Development has steadily declined, from above 60 years old to around 54 today. The average O.E.C.D. national leader is now two decades younger than Mr. Trump — and almost a quarter century younger than Mr. Biden…
And it isn’t just the American presidency that’s gone gray. The average age of Congress has trended upward for decades. Nancy Pelosi, the House speaker, is 80; Mitch McConnell, the Senate majority leader, is 78. The Supreme Court’s nine justices average above 67. Mr. Trump’s cabinet averages over 60, among the oldest in the O.E.C.D.
Here is one (not the only) explanation:
The way countries select their leaders offers a third possibility. In most O.E.C.D. countries, the head of government is a prime minister chosen by fellow lawmakers in the national legislature. Because party members pick their leaders, and can recall them at will, parliamentary systems give political parties significant control over whom to elevate, said Kaare Strom, a political scientist at the University of California, San Diego. And parties often have strategic reasons to pick younger leaders: to appeal to particular constituencies or to brand themselves behind more telegenic faces.
Presidential systems, by contrast, give parties less control over who from their ranks will run — and which candidate voters will prefer. “The process is more driven by who’s out there, who’s interested, and what kind of resources they have,” said Professor Strom. “There’s not the same kind of institutional control and vetting of those candidates that you have in the European parliamentary systems.”
Accumulated wealth and fundraising connections may matter more too in the American system, also favoring seniority. Here is the full NYT story by Ian Prasad Philbrick.