A new study (PDF) by Eric Ulken of the USC Annenberg School of Communication looks at political bias in the Google News aggregator.

The results?

… the findings … may be of interest given the ongoing debate about the quality of Google News’s sources. While my analysis does not indicate an overall conservative or liberal slant, it does confirm Lasica’s suspicion that non-traditional news sources are injecting ideologically biased articles into Google News search results.

…

…almost all of the additional bias in articles returned by Google News searches can be attributed to the site’s use of non-traditional news sources. In other words, if we consider only sources affiliated with old-media companies, the average bias scores for articles on Google News and Yahoo News are virtually identical.

If, like me, you use Google News a lot, you will also be interested in Private Radio’s study of Google News’s notoriously secret list of news sources. The source list for Google News UK is here.