Has the National Do Not Call Registry Helped or Hurt State-Level Response Rates? A Time Series Analysis

By the end of the initial registration period on August 31, 2003, the National Do Not Call Registry (DNC Registry) had registered more than 50 million telephone numbers. Approximately 18 months later that number had increased to more than 91 million. The impact of the DNC Registry on survey response rates, however, is largely unknown. Some researchers speculate that the registry could make it easier to distinguish between telephone survey interviewers and telemarketers. Other researchers argue that a significant portion of DNC registrants may not make such distinctions and would prefer instead to reduce all unsolicited calls from marketers and interviewers alike. Case outcomes from nearly 4.5 million telephone numbers called between January 1, 2002, and June 30, 2005, as part of the Behavioral Risk Factor Surveillance System were analyzed. Using trend analyses and autoregressive integrated moving average (ARIMA) time series model- ing, we assessed the impact of the DNC Registry on state-level monthly response rates in 47 states. Our findings indicate that once pre-DNC Registry trends in response rates and other potential covariates are accounted for, the national Do Not Call rules have had no significant impact on state-level response rates in either a positive or negative direction.