Congressional delegations that lasted the whole decade

[Nichlemn]

In redistricting, we often hear about how a new Congressional map has all seats "solid for the incumbent party for the whole decade". But how often did that actually occur last time?

States that never had a House seat change party hands:

Alaska (At-large)
Maine
Massachusetts
Montana (At-large)
Nebraska
Oklahoma
Oregon
Utah (but not as intended)
Vermont (At-large) (Counting Sanders as D)
Wyoming (At-large)

So only ten states never had a House seat change hands, and four of them were at-large (so redistricting had no role to play). One (Utah) was meant to be 3-0 for the decade but ended up 2-1. All states were either one party only or had a single off-party Congressman.

Adding Senators and #1, #3, #4, #7 and debatedly #9 come off the list, leaving just five states with no party changes.

So be sceptical about claims of a lock-safe map.