Former Louisiana Sen. Mary Landrieu has, as predicted in this piece which originally ran in December 2014, inked a deal at a DC lobbying firm. In light of her decision, we're re-publishing this look at how often that happens.

"K Street woos Mary Landrieu," Politico's headline reads. K Street, as you probably know, is the bucolic lane in Washington, DC that is home (at least symbolically) to most of the city's lobbying firms. And Mary Landrieu, as you also probably know, is the current-but-not-for-long Demcoratic senator from Louisiana who lost her reelection bid last weekend. (If you don't know what "woos" means, here you go. Now you can read the whole sentence!)

For readers, probably to a person, the response to the headline is: of course. Of course a former member of Congress is going to become a lobbyist. That's what always happens. Which is where your friends at The Fix come in. We decided to try to figure out just how true that is.

In a perfect world, "lobbying" and "lobbyist" are terms with clear, agreed-upon definitions. So-and-so is a lobbyist, we could say, and lobbies for such-and-such. Earlier this year, however, we were reminded that this is not the case.

Scott Brown's bid for the Senate in New Hampshire got mired in a very weird fight just before the state's Republican primary. An outside group, Mayday PAC, sent out a mailer calling him a "former Washington lobbyist," a characterization that Brown's campaign, instead of ignoring, decided to fight. So we all spent a lot of time figuring out exactly how Brown was defining "lobbyist" so that it didn't apply to the work he did for a lobbying firm. The upshot: It depends, that magical phrase that's so core to analysis! It depends on how much time he spent lobbying, if any, and who he talked to, if anyone. He didn't meet the legal definition of lobbyist.

You'll remember that Members of Congress are not allowed to become for-real, official, registered lobbyists as soon as they step off of Capitol Hill. Technically, lawmakers are supposed to wait two years before they can become registered lobbyists. But registration only kicks in after a certain amount of lobbying takes place, and doesn't prevent people from, say, going to work for lobbying firms or advising firms that lobby the government on best practices.

If you look at the Center for Responsive Politics' list of lobbyists from the 112th Congress, you can see the various lines that are drawn. Some former members of Congress are registered lobbyists. Some work for lobbying firms. Some work for places that lobby on particular issues. We took that data, the data from the 111th Congress, and the group's overall list of former members to figure out how many of those that left Congress each year are now Lobbyists or Employed in Possibly Lobbying-Related Fields. The answer is: A lot, but maybe not as many as you might think.

The ugh, of course reaction that you (or at least I) had to the Landrieu article isn't only because members of Congress often become lobbyists. It's because movement back-and-forth from lobbying firms to government happens among staff and among members of the military and pretty much all over. A 2011 report estimated that 400 former legislators had done lobbying. Earlier this year, the New York Times published a graph suggesting that lobbying firms are largely comprised of people with government experience.

If Landrieu does end up lobbying, then, she'll at least probably know some of her new coworkers. She won't know everyone, and this year's other unlucky senators won't all head to K Street. But at least any that do will feel right at home.