Sporting event attendance is determined by ex ante expectations about the quality of the game, but because changing television channels costs nothing, sporting event viewership is influenced by actual game progression. This implies that demand determinants for televised baseball may change as games progress. This study examined the dynamic relationship between demand for televised baseball games and the uncertainty of outcome hypothesis (UOH). In particular, we analyzed inning-varying coefficients in a television rating regression equation. According to our empirical study, there are large dynamics in TV viewership demand for sports events and the marginal effects of factors on viewership changes significantly as innings progress. The estimation results can be summarized as (1) the UOH was shown to be significant not only statistically but also economically; (2) although ex ante variables were more effective in earlier innings and ex post variables were more effective in later innings, we found that ex ante expectations of outcome uncertainty remain significantly influential in later innings; and (3) after the matchup, the ex ante game quality is the second most significant factor among the examined effects on ratings.