up until the 1990s, studies using indirect measures of the person and environment typically operationalized fit by combining the measures into a single index representing the difference between the person and environment (edwards, 1991; kristof-brown et al., 2005). despite their intuitive appeal, difference scores are plagued with numerous conceptual and methodological problems, such as reduced reliability, conceptual ambiguity, confounded effects, untested constraints, and reducing an inherently three-dimensional relationship between the person, the environment, and the outcome to two dimensions (cronbach, 1958; edwards, 1994; johns, 1981). these problems undermine the interpretation of the results of person-environment fit studies that rely on difference scores. similar problems apply to studies that operationalize fit using profile similarity indices that compare the person and environment on multiple dimensions (edwards, 1993).