In a 2004 study, Tim Groseclose and Jeff Milyo argue the "Journal" news pages have a pro-liberal bias because they more often quote liberal think tanks. They calculated the ideological attitude of news reports in 20 media outlets by counting the frequency they cited particular think tanks and comparing that to the frequency that legislators cited the same think tanks. They found that the news reporting of "The Journal" was the most liberal (more liberal than NPR or "The New York Times"). The study did not factor in editorials. Mark Liberman criticized the model used to calculate bias in the study and argued that the model unequally affected liberals and conservatives and that "..the model starts with a very peculiar assumption about the relationship between political opinion and the choice of authorities to cite." authors assume that "think tank ideology [...] only matters to liberals."