We all know that primary races don't see a whole lot of turnout. But it's still always shocking to see exactly how few people end up making decisions for the rest of the population.

Take Tuesday's upset in Virginia's 7th Congressional District, in which Dave Brat beat House Majority Leader (for now) Eric Cantor (R). A total of 65,000 people went to the polls, more than Cantor's campaign was expecting. But in a district that has 738,000 residents (according to the Census Bureau), that's only 8.8 percent of the population represented. And Brat only got a little over half of that vote.

Let's visualize it.

If you prefer, here's the breakdown by percentage. The voting age population is 73.6 percent of the district's population, but only 64.3 percent of the population is registered. And only 8.8 percent of the entire population voted. And 4.9 percent, one out of every 20 people that lives in Virginia's 7th Congressional District, voted for the man who will almost certainly be its next representative in Congress.

% of VA-7 population % of Voting age % of Registered % of Primary voters
Voting age 73.6 percent
Registered voters 64.3 87.4
Primary voters 8.8 12.0 13.7
Brat voters 4.9 6.6 7.6 55.5

Data sources: Census Bureau, Virginia Board of Elections, Associated Press voting results. Since Virginia doesn't have party registration, the number of Republicans was estimated by applying the 2012 vote for Mitt Romney in the district to the registered voter population.