Karl Deutsch has argued that since the mid-1950's the structural, or institutional, political integration of Western Europe has come to a halt. What Deutsch means by the halt of political integration in Western Europe is the ending of any trend toward the development or the expansion of the authority of supranational institutions to make major policy decisions. Political decisions will continue to be made by sovereign nationstates and not by any supranational European institutions. Although institutional political integration is the central variable in his analysis, Deutsch reports no attempts to directly measure the decisionmaking capability of any Western European supranational institution. By accepting the validity of his sociocausal paradigm of political integration, which holds that political integration cannot occur until after a process of social assimilation creates a homogeneous transnational population, Deutsch contends that in order to describe the levels of political integration in Western Europe he need only examine data relating to the levels of social homogeneity which characterize that region. To measure the extent of social assimilation in Western Europe Deutsch examines the transaction flow rates of trade, mail, travel, migration, and student exchange data and studies the responses of mass and elite population samples to a complex series of survey questions. Deutsch's analysis of these varied data leads him to conclude that the levels of social assimilation in Western Europe have 1) remained constant for the past decade and 2) are too low to permit institutional political integration to occur.