For all the complaints you hear, internet reading is much less segregated than the networks of our work, family, and friends (all given formal measurements in the paper). Jesse Shapiro and Matt Gentzkow report:
We use individual and aggregate data to ask how the Internet is changing the ideological segregation of the American electorate. Focusing on online news consumption, offline news consumption, and face-to-face social interactions, we define ideological segregation in each domain using standard indices from the literature on racial segregation. We find that ideological segregation of online news consumption is low in absolute terms, higher than the segregation of most offline news consumption, and significantly lower than the segregation of face-to-face interactions with neighbors, co-workers, or family members. We find no evidence that the Internet is becoming more segregated over time.
Here are some details:
The average Internet news consumer’s exposure to conservatives is 57 percent, slightly to the left of the US adult population. The average conservative’s exposure is 60.6 percent, similar to a person who gets all her news from usatoday.com. The average liberal’s exposure is 53.1 percent, similar to a person who gets all her news from cnn.com. The isolation index for the Internet is 7.5 percentage points, the difference between the average conservative’s exposure and the average liberal’s exposure.
News consumers with extremely high or low exposure are rare. A consumer who got news exclusively from nytimes.com would have a more liberal news diet than 95 percent of Internet news users, and a consumer who got news exclusively from foxnews.com would have a more conservative news diet than 99 percent of Internet news users.
…Visitors of extreme conservative sites such as rushlimbaugh.com and glennbeck.com are more likely than a typical online news reader to have visited nytimes.com.
This is one of the best papers on on-line media.