Media conglomerates often own newspapers and other media, while also making films, releasing music, publishing books and so on. Unsurprisingly, they are often accused of pressuring their news media to review these entertainment media more favourably than they otherwise would, and this suspicion seems quite reasonable at first blush. But a new paper finds no evidence that this is true at all for movies. "Does Media Concentration Lead to Biased Coverage? Evidence from Movie Reviews" by economists Stefano DellaVigna and Johannes Hermle say there is not even evidence of a tiny effect and suggest this means reputational effects are very important for newspapers:

Media companies have become increasingly concentrated. But is this consolidation without cost for the quality of information? Conglomerates generate a conflict of interest: a media outlet can bias its coverage to benefit companies in the same group. We test for bias by examining movie reviews by media outlets owned by News Corp.–such as the Wall Street Journal–and by Time Warner–such as Time. We use a matching procedure to disentangle bias due to conflict of interest from correlated tastes. We find no evidence of bias in the reviews for 20th Century Fox movies in the News Corp. outlets, nor for the reviews of Warner Bros. movies in the Time Warner outlets. We can reject even small effects, such as biasing the review by one extra star (our of four) every 13 movies. We test for differential bias when the return to bias is plausibly higher, examine bias by media outlet and by journalist, as well as editorial bias. We also consider bias by omission: whether the media at conflict of interest are more likely to review highly-rated movies by affiliated studios. In none of these dimensions we find systematic evidence of bias. Lastly, we document that conflict of interest within a movie aggregator does not lead to bias either. We conclude that media reputation in this competitive industry acts as a powerful disciplining force.

The whole thing is very clear in a chart—newspapers owned by News Corp are about as positive about Fox films as those owned by Time Warner (and vice versa). So much for media bias, eh!