The effects of response rate changes on the index of consumer sentiment.

From 1979 to 1996, the Survey of Consumer Attitudes response rate remained roughly 70 percent. But number of calls to complete an interview and proportion of interviews requiring refusal conversion doubled. Using call-record histories, we explore what the consequences of lower response rates would have been if these additional efforts had not been undertaken. Both number of calls and initially cooperating (vs. initially refusing) are related to the Index of Consumer Sentiment (ICS), but only number of calls survives a control for demographic characteristics. We assess the impact of excluding respondents who required refusal conversion (which reduces the response rate 5-10 percentage points), respondents who required more than five calls to complete the interview (reducing the response rate about 25 percentage points), and those who required more than two calls (a reduction of about 50 percentage points). We found no effect of excluding any of these respondent groups on cross-sectional estimates of the ICS using monthly samples of hundreds of cases. For yearly estimates, based on thousands of cases, the exclusion of respondents who required more calls (though not of initial refusers) had an effect, but a very small one. One of the exclusions generally affected estimates of change over time in the ICS, irrespective of sample size.