President Donald Trump (C) gathers with Congressional Republicans in the Rose Garden of the White House after the House of Representatives approved the American Healthcare Act, to repeal major parts of Obamacare and replace it with the Republican healthcare plan, in Washington, U.S., May 4, 2017.

House Judiciary Committee Chairman Bob Goodlatte of Virginia announced Thursday that he will retire from Congress next year, the latest member to join the more than two dozen Republicans who've confirmed they won't be returning to Congress in 2019.

"With my time as Chairman of the Judiciary Committee ending in December 2018, this is a natural stepping-off point and an opportunity to begin a new chapter of my career and spend more time with my family," Goodlatte said in a statement.

Retirements in Congress, as in any other job, are part of the natural workplace cycle. But given the nature of politics, they're often carefully timed to benefit lawmakers' future careers. This is especially true in the House, where members must win re-election every two years.

According to Roll Call, an average of 22 House members retire every cycle. So far in the 2018 cycle, that number has jumped to 30 — 21 Republicans and nine Democrats, with more retirements expected later this month.

And while it's tempting to blame the polarizing effect of President Donald Trump on the nation, or the infighting that plagues the House Republican caucus, there's more to it than that.

CNBC is keeping a tally of all the House retirements, sorted into groups based on the reasons behind members' decisions, and what the retirements mean for both parties. Below is the latest.

Half of the House members who've announced they're retiring next year, 15 of the 30, are leaving to run for governorships or Senate seats in their home states, and among those running for governor there's an even party split: five Democrats and five Republicans.

Democratic Reps. Jared Polis, Colo.; Colleen Hannabue, Hawaii; Tim Walz, Minn.; John Delaney, Md.; and Michelle Lujan Grisham, N.M., have all thrown their hats in the ring, as have Republicans Kristi Noem, S.D.; Steve Pearce, N.M.; Diane Black, Tenn.; Raul Labrador, Idaho; and Jim Renacci, Ohio.

Another six House members are leaving to run for Senate seats: four Republicans and two Democrats.