For as long as hot lead has been used to make metal type, the model for generating news has been top-down: editors determined what information was important and then shared it with the masses. But with the advent of technology that allows media companies to identify what kind of content readers want, that model is becoming inverted. The latest and perhaps broadest effort yet in democratizing the news is under way at Yahoo, which on Tuesday will introduce a news blog that will rely on search queries to help guide its reporting and writing on national affairs, politics and the media. Search-generated content has been growing on the Internet, linked to the success of companies like Associated Content, which Yahoo recently bought, and Demand Media, which has used freelance writers to create an online library of more than a million instructional articles. Yahoo software continuously tracks common words, phrases and topics that are popular among users across its vast online network. To help create content for the blog, called The Upshot, a team of people will analyze those patterns and pass along their findings to Yahoo’s news staff of two editors and six bloggers. The news staff will then use that search data to create articles that — if the process works as intended — will allow them to focus more precisely on readers.