AGENDA DIVERSITY AND AGENDA SETTING FROM 1956 TO 2004 What are the trends over time?

Using aggregate time-series data, this study tests four research hypotheses. First, we examine the long-term trend in the issue agenda diversity of the public as measured by the Gallup Most Important Problem question from 1956 to 2004. Second, we test whether the agenda-setting effect between the media agenda and the public agenda has become weaker over that time. Finally, with multivariate autoregressive integrated moving average (ARIMA) modeling, this study investigates the causal relationships among the longitudinal changes in public agenda diversity, the New York Time's content diversity, and the New York Times' agenda-setting effect on public opinion. While no significant trend in the agenda-setting effect was found, we found a significant quadratic trend in public agenda diversity and significant causal relationships among these three time-series measures. In short, increased public agenda diversity decreased the New York Times' public agenda-setting effect, and the issue agenda diversity of the New York Times has decreased over time, but the overall agenda-setting effect between the New York Times and the public has not become weaker over time.