Effects of response cost on the behavior of a million persons: charging for directory assistance in Cincinnati.

An interrupted time-series analysis of local directory-assistance calls in the Cincinnati area from 1962 to 1976 revealed a significant reduction in the daily frequency of calls after charges were introduced in 1974. No reductions occurred in the daily frequency of long-distance directory-assistance calls, which remained free. The results attest to the efficacy of response-cost procedures with large subject populations in the natural environment. The applicability of response-cost procedures to social and business problems is discussed.