تمرکز بازار رسانه ، سطوح تبلیغات و قیمت آگهی

Standard media economics models imply that increased platform competition decreases ad levels and that mergers reduce per-viewer ad prices. The empirical evidence, however, is mixed. We attribute the theoretical predictions to the combined assumptions that there is no advertising congestion and that viewers single-home. Allowing for crowding in viewer attention spans for ads may reverse standard results, as does allowing viewers to multi-home.

When Fox television entered the US market, advertising levels on NBC, CBS, and ABC rose from 7 minutes per hour in 1989 to around 9 minutes in 1998.2 This suggests that entry may induce higher ad levels. However, standard models of advertising-financed media platforms, such as Anderson and Coate (2005), predict that entry should lower ad levels (and raise per-viewer ad prices). They also predict that mergers should have the opposite effect, of raising ad levels and lowering ad prices.3 Some support for this standard prediction is provided by the radio industry executive cited in Anderson and Coate (2005), who argued that ad levels rise after a merger. Some empirical studies indicate predictions opposite from the standard theory. Focusing on local radio markets, Brown and Williams (2002) find that local ownership concentration slightly increases ad prices. Brown and Alexander (2005) report a similar result in the TV market (interestingly, they find that the ad volume might increase as well). Jeziorski (2011) finds that ad levels fall with concentration. Most studies indicate mixed evidence or no clear-cut result in one or the other direction. Chipty (2006) finds no systematic relationship between ownership structure and ad prices (or ad levels). Sweeting (2010) investigates advertising levels using a panel of data from music stations based on airplay data from 1998 to 2001. He does not find clear evidence of a relationship between ownership of several stations and the advertising level. In a structural analysis of two-sided radio markets, Tyler Mooney (2011) finds that ad prices and ad volume may increase or decrease with concentration.4

Standard media economics theory cannot accommodate the possibility that mergers lower ad levels and raise ad prices, or that entry has the opposite effects. Empirical evidence is mixed, so the unambiguous results from the standard theory suggest that some countervailing forces may be missing. In this paper we have explored the implications of advertising congestion and viewer multi-homing and found that the predictions of the standard theory are reversed. The two departures from standard theory that we have explored may well fit different media markets, and thus could be seen as complementary (as opposed to competing) explanations. In Anderson and Peitz (2011), access to viewer attention is limited and viewers mix between channels. The model seems well-suited for television and radio insofar as viewers have a fixed amount of time to allocate among channels, and cannot see the ad currently aired on one channel if they are on another at the time the ad is aired. By contrast, in Anderson et al. (2010), multi-homing viewers are fully exposed to the advertising of more than one media platform. This better fits magazines and newspapers, where viewer (or readers) can be exposed simultaneously to the ads of more than one platform.