People constantly tell me that term limits are needed in the Congress to ensure new faces and ideas on Capitol Hill. And I always tell people that there is more turnover than they realize in the House and Senate.

But even I was surprised when I went back to check the numbers from recent years.

On Monday, yet another Senator decided to move on, as Sen. Mike Johanns (R-NE) announced he would not seek re-election in 2014, meaning that five Senators are already opting for retirement - and one Senate seat has already changed hands this year with the retirement of Sen. John Kerry (D-MA).

Are we on a faster pace than recent years? I decided to check.

I went back six years, which is the length of one Senate term, to get an idea of how things have changed with the 2008, 2010 and 2012 elections - along with the usual smattering of resignations and deaths in the Senate family.

In the 110th Congress, which included 2007 and 2008, 12 seats changed hands because of election defeats, retirements, resignations and death.

From 2009-2010 in the 111th Congress - without double counting changes in seats that had appointees from Illinois, Delaware, Florida, Massachusetts and West Virginia - you had 16 seats changing hands.

Then in the last two years, during the 112th Congress from 2011-2012, 15 Senate seats changed hands (though for counting purposes, the Scott Brown seat in Massachusetts shouldn't be counted again, so I'll score it as 14.)

If you're keeping score, that's 42 Senate seats with different names in less than six years. 42% of the Senate.  Make it 43 with the replacement for Kerry.

Let me repeat that - over 40% of the Senators now serving have not been in office for one full Senate term, six years.  

Whether you think that term limits are needed or not - the voters, Senators themselves, and the Grim Reaper are all doing a solid job of adding in new blood to the World's Greatest Deliberative Body.

And by the time we get to the November 2014 elections, that number will go up even more, likely ensuring that over half of the seats in the Senate will have had turnover in a period of just over seven years.

Term limits? Looks like they're already happening in the Senate.