California Gov. Jerry Brown, a spry 76-year-old. (AP Photo/The Sacramento Bee, Jose Luis Villegas)

California's leading Democrats are remarkable specimens of longevity. The state's two senators are 73 and 81. Gov. Jerry Brown is 76. Rep. Nancy Pelosi, perhaps the best known Democrat in the state, is 74. Between the four of them, they've held their current positions for over eight decades.

But a "political shakeup looms," Politico wrote Monday, with young upstarts looking to replace the state's longstanding party leadership. So what's the story here? Is it that, like the rest of the country, politicians are living longer and staying on the job for more years than previous generations, stimieing younger politicians who want to advance?

In case the headline didn't give it away: probably not. Instead, California's younger Democrats are being held back by the same thing that holds mid-tier politicians back everywhere. Incumbency. It's not really the average 76 years those politicians have been alive. It's the 81 combined years they've been in office.

We pulled data on the age of Congress and the age of the population on the whole to see how the two correlated. And looking at it roughly, the median age of the population and of the workforce has ticked up at about the same pace in recent years as has the average age of Congress. The workforce is understandably older than the population (those darn child labor laws ruined everything), but Congress is somewhat remarkably older than the rest of the labor force.

In part, that's because it usually takes a while to get to Congress. You often have to win lower office first, build relationships in the community, become financially stable in your personal life, and so on. And, much more importantly -- you have to wait for a chance to run.

We'll come back to that. First, an important point. The median age of members of Congress in 1989 was 52.8. So what would you guess was the average age in 1969? If the trend above is an actual trend, you'd figure, what, 45? Well, no. It was 53.

Slate had a good look at the fluctuations in the age of Congress over time when the 113th Congress took office in 2013. That Congress was fairly old, though younger than the 111th, which was the oldest Congress ever. But this, the site's Brian Palmer wrote, is a function of variations in politics, not populations. The House was once seen as a stepping stone to higher office, which led to shorter terms. The transition to seniority-based positions of power made sticking around more worthwhile. And, of course, a dramatic anti-incumbent fervor could do remarkable things for the average age of Congress.

That's because winning a seat in Congress depends on a lot of elements falling into place for a politician. It's not as though there's only one qualified candidate in every congressional district. Every place has scads of city council members or state senators or assembly members or selectmen and -women or any number of other elected officials who are waiting for a vacancy or a moment of weakness to challenge an incumbent. Often, any speculation about imminent retirement or a plunge in poll numbers leads to behind-the-scenes jockeying to line up support just in case. The number of things that need to fall into place for even a qualified, popular politician to win higher office is remarkable. In California, Sens. Barbara Boxer and Dianne Feinstein have been working later in their lives than a lot of Americans. But they've also been consistently reelected and enjoy broad support in the state.

There's a giveaway to this point in that Politico article. Among those champing at the bit for an opportunity to step up are Attorney General Kamala Harris, 49, Lt. Gov. Gavin Newsom, 46, and ... former Los Angeles mayor Antonio Villaraigosa, 61.

These kids today just can't get a chance.