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Some political scientists gauge ideology by comparing the annual ratings by the Americans for Democratic Action (ADA) with the ratings by the American Conservative Union (ACU). Biden has a lifetime liberal 72% score from the ADA through 2004, while the ACU awarded Biden a lifetime conservative rating of 13% through 2008. Using another metric, Biden has a lifetime average liberal score of 77.5%, according to a National Journal analysis that places him ideologically among the center of Senate Democrats as of 2008.
