Within the last several years, new data have become available to test the various theoretical models of EU decision-making, and, in doing so, to assess actor influence. This article examines the extent to which the recent DEU and DEUII datasets provide sufficient information to distinguish between competing theoretical models of legislative decision-making, and accurately assess the power of the different branches of EU government. It argues that insufficient attention has been paid to measurement error in these data. Once measurement error is accounted for, it becomes clear that these data do not provide sufficient information to distinguish between most models of legislative politics. Moreover, empirical models that fail to account for measurement error are likely to lead researchers to erroneous conclusions about actors’ legislative influence.