Look out, Nielsen. The TV ratings giant took a hit this morning with Tribune’s announcement  that its 42 TV stations will use Rentrak to provide audience measurement data —  including for their TV Everywhere streaming efforts. Before this deal, Tribune just used Rentrak at its stations in Cleveland and Des Moines.

The new agreement boosts the number of stations Rentrak serves by more than 10% to 430. Now with about 20% of TV stations, Rentrak “has all but won the market for local TV ratings from Nielsen,” says Brean Capital’s Todd Mitchell. Rentrak’s selling point: It can help stations reduce advertising make-goods which can account for as much as 15% of revenues “due to the instability of Nielsen’s ratings in these poorly sampled markets,” the analyst says.  He also cites Rentrak’s “aggressive pricing model” vs Nielsen.

Today’s announcement says that the company will provide Tribune stations with a “full suite of local market ratings services, including its automotive and political Advanced Demographics.”

Tribune Broadcasting’s Larry Wert says that Rentrak offers “consumer behavior insight from a significant measurement footprint in each market.” That will “help our stations make more informed decisions and provide our clients with detailed audience viewing information.”