Media bias in the United States occurs when US media outlets skew information, such as reporting news in a way that conflicts with standards of professional journalism or promoting a political agenda through entertainment media. There is liberal bias and conservative bias. Claims of outlets, writers, and stories exhibiting both have increased as the two-party system has become more polarized. There is also bias in reporting to favor the corporate owners, and mainstream bias, a tendency of the media to focus on certain "hot" stories and ignore news of more substance. A variety of watchdog groups attempt to combat bias by fact-checking biased reporting and unfounded claims of bias. Researchers in a variety of scholarly disciplines study media bias.