A map that shows we really do live in two different Americas

Story highlights

  • More than half of all Congressional districts are safe for one of the two parties
  • People don't live, work or socialize around others who have different political views

(CNN)If you're like most Americans, you don't live around or socialize with people with whom you disagree with politically. This self-sorting by political ideology is why so many people were shocked Donald Trump won last November ("But I don't know anyone who voted for him") while half(ish) of the country knew it was happening all along.

A new map courtesy of the Cook Political Report shows just how divided we are along partisan lines. Here it is:
The map shows two things: 1) How few competitive districts there are in the country and 2) just how geographically isolated we are, politically speaking.
First, a bit of explanation. The Cook Political Report assigns each of the 435 House districts a Partisan Voting Index (PVI) score that seeks to compare how each seat performs politically against every other seat. A seat with a PVI of R+8, for example, means that the district performed eight points more Republican than the national average in the 2016 presidential election.
Generally speaking, a district with a PVI score between R+5 and D+5 is considered competitive. Seats with a PVI of +10 (or more) for either side are generally regarded as safe.
According to calculations made by the Cook Political Report's David Wasserman, there are lots more of those sorts of seats than there were in 1997. Twenty years ago, there were 81 seats with a PVI of D+10 and 76 with an PVI or R+10. Today, there are 118 seats with a PVI of D+10 and 133(!) seats with a PVI of R+10.
A little math yield this: In 1997, there were 157 "safe" seats in Congress -- or about 36% of the entire House. Now there are 251, which constitutes almost 58% of all congressional districts.
That's bad enough! But, one look at the Cook map above shows that not only do we tend not to live in the same congressional districts with people about whom we disagree on politics and policy, but we often don't even live in the same state or region.
The entirety of the Midwest and Upper Plains are filled with solidly Republican House districts. Both coasts are stacked with heavily Democratic districts. The areas with even marginal competition in them -- Mid-Atlantic, Southwest -- are shrinking.
It's hard to overstate how self-sorting has fueled polarization -- in our media, in our news consumption, in our lives -- over the past decade or two. When you never run into anyone who you respect but who disagrees with you on something, and you never watch anything that challenges your beliefs, you become convinced that what you think is a) what everyone should think and b) totally, 100% right.
You also tend to vote for members of Congress who reflect your views and regard any attempts by those elected officials to work with colleagues across the aisle as capitulation. You punish those who stray from rigid ideology. And then you complain why Congress can't get anything done.
So, yeah.