An increasingly high number of retirements in the Senate means the chamber will continue to feature a striking number of new faces as the old bulls are replaced with newcomers.

But even as the the new blood continues to flow in, the Senate isn't getting much younger.

Sen. Carl Levin's (D-Mich.) announcement Thursday that he would retire makes him the seventh senator to announce his exit so far this year. The number of Senate retirements over the past three election cycles (25) is already tied for the second-most since the 1970s and could wind up setting a new record.

Most of those retirements have come from long-time senators. The 78-year-old Levin is the fifth septuagenarian (at least 70 years old) or above to retire in 2014. That matches the number of old-bull senators who retired in 2012.

But a funny thing happened on Election Day 2012. Despite all those senior citizens retiring from the upper chamber, the average age of the Senate declined only by the slightest of margins, from 62.2 years to 62.0 years, according to the Congressional Research Service.

And in fact, over the past decade-plus, the Senate has gotten a couple years older than it was before.

The reason is that even as recently retired senators like 86-year-old Daniel Akaka (D-Hawaii), 77-year-old Herb Kohl (D-Wis.) and 71-year-old Ben Nelson (D-Neb.) head for the exits, plenty of the newly elected senators come from an older generation as well.

Newly elected Sen. Angus King (I-Maine), for example, is 68. And fellow freshman Sens. Mazie Hirono (D-Hawaii), Elizabeth Warren (D-Mass.) and Deb Fischer (R-Neb.) are all in their 60s. Four senators elected in 2010 were also in their 60s.

The cumulative effect is that the senators who remain in the chamber get two years older, and the new senators aren't that much younger than the people they replaced.

In other words, we still have a Senate populated by old people. It might get a little bit younger with people such as Levin and 89-year-old Sen. Frank Lautenberg (D-N.J.) heading for the exits, but it's still going to be an older chamber than it was a decade ago.

The difference is that, while the age is still there, the institutional memory no longer is. While six years ago, 44 senators had served at least three terms, that number is now down to 32 (and is likely to drop further after the 2014 election).

In addition, at the start of the current Congress, more than half of senators had served one full term or less. Levin's exit means that will happen again in 2015, when it's already guaranteed that 50 members will have served one term or less.

So while the old people remain, the old ways may not. And that may hearten people who would like to reform how the Senate operates or want to see some change in Washington.