The cumulative effect over time has resulted in a U.S. House where today only about two dozen of the 435 seats are considered competitive by non-partisan election analysts, and Republicans — who controlled more state legislatures in 2012 when the current maps were approved — are favored to maintain control of the House until the next reapportionment round ahead of the 2022 congressional elections.

via Democrats introduce bill to end gerrymandering.

And there you have it.  More stats and data on this (hopefully) soon.