There is a broad consensus that news media outlets incorporate ideological
biases in their news articles. However, prior studies on measuring the
discrepancies among media outlets and further dissecting the origins of
semantic differences suffer from small sample sizes and limited scope. In this
study, we collect a large dataset of 1.8 million news headlines from major U.S.
media outlets spanning from 2014 to 2022 to thoroughly track and dissect the
semantic discrepancy in U.S. news media. We employ multiple correspondence
analysis (MCA) to quantify the semantic discrepancy relating to four prominent
topics - domestic politics, economic issues, social issues, and foreign
affairs. Additionally, we compare the most frequent n-grams in media headlines
to provide further qualitative insights into our analysis. Our findings
indicate that on domestic politics and social issues, the discrepancy can be
attributed to a certain degree of media bias. Meanwhile, the discrepancy in
reporting foreign affairs is largely attributed to the diversity in individual
journalistic styles. Finally, U.S. media outlets show consistency and high
similarity in their coverage of economic issues.

通过采用多重对应分析 (MCA) 测量及洞悉 2014 年至 2022 年间 1.8 百万份美国主要媒体新闻头条的语义差异，该研究发现美国国内政治和社会问题的媒体报道存在一定程度的媒体偏见，而外交报道的偏差主要来自个人的新闻风格多样性，而在经济问题的报道上，美国媒体呈现出一致性和高度相似性。