Agenda-setting theory describes the "ability [of the news media] to influence the salience of topics on the public agenda." That is, if a news item is covered frequently and prominently, the audience will regard the issue as more important. Agenda-setting theory was formally developed by Max McCombs and Donald Shaw in a study on the 1968 American presidential election. In the 1968 "Chapel Hill study," McCombs and Shaw demonstrated a strong correlation coefficient (r > .9) between what 100 residents of Chapel Hill, North Carolina thought was the most important election issue and what the local and national news media reported was the most important issue. By comparing the salience of issues in news content with the public's perceptions of the most important election issue, McCombs and Shaw were able to determine the degree to which the media determines public opinion. Since the 1968 study, published in a 1972 edition of Public Opinion Quarterly, more than 400 studies have been published on the agenda-setting function of the mass media, and the theory continues to be regarded as relevant.