In 2010, Silver wrote an article entitled "Is Rasmussen Reports biased?" in which he mostly defended Rasmussen from allegations of bias. However, later in the year, Rasmussen's polling results diverged notably from those of other mainstream pollsters, which Silver labeled a "house effect." He went on to explore other factors that may have explained the effect, such as the use of a likely voter model, and claimed that Rasmussen conducted its polls in a way that excluded the majority of the population from answering.