This paper examines the trend of ownership diversity in broadcast TV programming, and the influence of vertical mergers on ownership diversity. Number of programs and programming hours were used to measure ownership diversity on primetime networks. Programming data for 14 weeks in 1993-2006 were analyzed using an ANOVA and a Chow test. The results from empirical analysis imply that there are no significant effects of vertical mergers on affiliated programming hours. The findings do not seem to support the view that vertical mergers might harm the diversity of primetime programming.