Replication Data for: Local News and National Politics

The level of journalistic resources dedicated to coverage of local politics is in a long term decline in the US news media, with readership shifting to national outlets. We investigate whether this trend is demand- or supply-driven, exploiting a recent wave of local television station acquisitions by a conglomerate owner. Using extensive data on local news programming and viewership, we find that the ownership change led to 1) substantial increases in coverage of national politics at the expense of local politics, 2) a significant rightward shift in the ideological slant of coverage and 3) a small decrease in viewership, all relative to the changes at other news programs airing in the same media markets. These results suggest a substantial supply-side role in the trends toward nationalization and polarization of politics news, with negative implications for accountability of local elected officials and mass polarization.美国新闻媒体中，用于地方政治报道的新闻采编资源长期呈下滑态势，受众群体逐渐转向全国性媒体平台。本研究借助某企业集团近期收购地方电视台的行业事件，旨在探究该趋势究竟由需求端还是供给端驱动。通过采集并分析涵盖地方新闻节目及收视情况的全面数据集，我们发现：相较于同一媒体市场内其他播出的新闻节目，此次所有权变更引发了三方面显著变化：1）大幅提升全国政治新闻的报道占比，同时以削减地方政治报道为代价；2）报道的意识形态倾向显著向右偏移；3）收视率小幅下滑。上述研究结果表明，在政治新闻的全国化与极化发展趋势中，供给端因素起到了重要推动作用，这对地方民选官员的问责机制以及大众政治极化均产生了负面影响。