Last week was the season finale for Fringe, the new J.J. Abrams show. The series had a strong first season, finishing even stronger than it started. The final episode had a total audience of 13.5 million viewers, a record high for the series and 45% higher than the season finale for Lost, perhaps an indication of which series is now taking the mantle.

It probably helped that the series had American Idol as its lead-in since January 20th, during its last 10 episodes. Note the substantial spring in the following graph.

Episodes that followed American Idol are demarcated by a light background in the following graph. Before January 20th, House was the lead-in at 8:00 p.m. It should also be noted that repeat episodes of Fringe are demarcated by a dark background in the graph, aired in October, December and January.

Looking at just new episodes of Fringe, it seems that American Idol boosted its total audience 18% more than House (also no ratings slouch), giving Fringe an extra boost during its infant season.

It is not surprising therefore that Fox anounced today that next season two of its most promiment new dramas, Past Life and Human Target, are respectively programmed Tuesday and Wednesday at 9:00 p.m., following American Idol.

Fringe, incidentally, is being cut loose of its training wheels, and moving on to Thursdays at 9:00 p.m., following Bones.

One of this year’s most promising shows, Fringe is widely considered to be returning next season due to its decent ratings. Some viewers have often said the show has benefited largely from its current lead-in, American Idol, which often surpasses 20 million viewers. In order to properly judge the ‘Idol Effect,’ I compiled all of the ratings for the current season of Fringe.

Looking at the current season to date, Fringe has averaged 8.9 million viewers per episode. Within the 18-49 and 18-34 demos, the show has averaged 4.75 and 2.02 million viewers respectively.

The dark areas in graph above, during late October and between early December and early January, are days that repeat episodes of Fringe were aired. The average total audience for these episodes is 5.1 million viewers, 42% less than the season average. The light areas are days that Fringe followed an episode of American Idol. These days the show had an average audience of 11.46 million, 29% greater than the season average. Note the change in lead-in audience the American Idol portion.

Since Fringe has not aired a single repeat episode after American Idol, I decided to look at only new episode ratings in order to properly gauge the ‘Idol Effect.’

Taking into account only new episodes, Fringe had an overall audience 18% greater after American Idol than after House. However, in the 18-34 and 18-49 demos the difference was much less, only 2% and 10% greater, respectively. I had imagined that the effect would be much greater in these younger demos where American Idol is very popular, but the younger audience simply dropped off at a greater rate.

In any case, both House and American Idol are popular shows, and it is evident that Fringe was well positioned in its premiere season to succeed.