Cooperation Rate

The cooperation rate to a survey indicates the extent to which contacted individuals cooperate with a request to participate in a survey. It is often mistakenly reported or interpreted as the response rate. Generally, the cooperation rate is the ratio of all cases interviewed out of all eligible units ever contacted, whereas a response rate is the ratio of all cases interviewed out of all eligible sample units in the study, not just those contacted.

The American Association for Public Opinion Research (AAPOR), which has established a standard definition of the cooperation rate, offers at least four ways to calculate it. The numerator includes all completed interviews but may or may not include partial interviews. The denominator includes all eligible sample units that were contacted (including refusals and other non-interviews that may have been contacted), but may or may not include sample units that are incapable of cooperating (e.g. because of health or language barriers).

When reporting the cooperation rate, researchers should clearly define the rules for survey eligibility and explain how they decided to calculate the rate. The level at which the rate has been calculated (individual, household, school district, business, etc.) should be reported. Though cooperation rates are most often calculated using only contacts with known eligible respondents, if there is a screener, consumers of survey results might also want to know the percentage of people who cooperate with the screener in addition to the percentage of people who participated in the full survey.

One important variation in how the cooperation rate is calculated is whether contacted sample members with unknown eligibility are included in the denominator of the calculation. It is possible to include in the denominator an estimate of all eligible cases (or e, the proportion of cases with unknown eligibility assumed to be eligible), not just the cases confirmed as eligible.

A lower cooperation rate implies a lower response rate, raising concerns about the representativeness of the participating sample members. For example, Robert Groves and Mick Couper report that some research has shown that noncooperating sample members score lower on social engagement indices than do cooperating sample members. If measures of social engagement are important analytical variables, then a low cooperation rate may bias survey estimates.

The cooperation rate also has implications for survey costs, as it is an indicator of sample yield (i.e. the number of completed interviews achieved from a fixed number of sample units). The lower the cooperation rate, the more the effort needed to achieve a required number of completed interviews, whether that effort involves enlarging the sample, making additional contacts to sample members, training interviewers, or providing incentives to increase cooperation. For interviewer-administered surveys, the cooperation rate serves as one measure of the interviewer's success.

Survey organizations try to maximize the response rate by maximizing the cooperation rate (in addition to maximizing the contact rate, or the proportion of all sample members for which a person was reached). For instance, researchers may try to alter the sample members' predisposition toward survey participation by changing the nature of the initial contact to make the survey more appealing. Very often, cooperation is manipulated through advance mailings and through the interviewer. The issue of interviewer-respondent interaction and its influence on survey cooperation has received considerable attention in the recent literature on survey research, thus motivating survey organizations to focus on interviewer training. The training generally emphasizes avoiding refusals, tailoring the interview approach to sample members, and maintaining the interaction with sample members while on the telephone or at the doorstep. Evidence from studies of interviewer training and interviewer-respondent interactions suggests that tailoring and maintaining interaction are important to maximizing cooperation rates.

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