Traditional statistical analyses of interviewer effects on survey data do not examine whether these effects change over a field period. However, the nature of the survey interview is dynamic. Interviewers' behaviors and perceptions may evolve as they gain experience, thus potentially affecting data quality. This paper looks at how interview length and interviewer evaluations of respondents change over interviewers' workloads. Multilevel models with random interviewer effects are used to account for the clustering of cases within interviewers and individual interviewer characteristics in the 1984, 1988, and 2000 National Election Studies. The 1984 and 1988 NES released sample in four replicates, minimizing the confound between order in an interviewers' workload and sample composition. We find that over the course of the studies, both measures change significantly. Interviewer prior survey experience also was significantly negatively related to the length of the interview. These findings have implications for interviewer training prior to and during studies, as well as suggesting future research to reveal why these behaviors and perceptions change
