When conducting market research, either through survey forms or another mode, the method of sending a survey pre-notification letter can be a tempting one.
For some time now survey methodologists have been conducting studies of pre-notification letters to determine if they have any affect, either positively or negatively, on survey response rates. An overall analysis of these various independent studies revealed an increase in response rate of approximately 8% when compared against studies where no pre-notification letter was sent.
No one can say for sure exactly why pre-notice survey letters seem to assist in increasing the number of survey responses, but perhaps they help to establish the legitimacy of a survey, contributing to a respondent's feeling of trust and the credibility of the organization conducting the research. Another possibility is that a pre-notice letter builds expectation of arriving mail (be it electronic, paper, or in-person). A third possibility is that a potential respondent is less likely to disregard the survey when it arrives if they are aware it is arriving shortly.
Although survey pre-notification letters are an excellent (but sometimes expensive) way to increase response rates, they are seldom used in marketing research surveys. Each researcher needs to weigh the additional cost of sending out a pre-notice to potential respondents against the probability of a lower response rate.
It's worthwhile to take your population's survey sample size into consideration when coming to this decision. When your sample sizes are small, each individual response affects your survey results even more. Increasing those responses through utilizing a pre-notice letter may counterbalance the increased cost of sending them out to your participants.