Measuring interstate variations in drug problems.

This article describes the Drug Problem Index (DPI), a composite index measuring the interstate severity of drug abuse problems. The DPI's components (drug-coded mortality, drug-defined arrest, and drug-treatment client rates) were selected because they were linked closely with drug abuse, data were available for all states, and there was published evidence of their validity. The variables were reliable, and their convergent validity was estimated in a multi-trait, multi-method matrix. We found evidence consistent with the DPI's construct validity in its relations with other consequences of drug abuse. The DPI correlated significantly with the Block Grant drug need index but not with model estimates of drug dependence based on the National Household Survey.