Key messages

Response to questionnaires can be increased by contacting people before they are sent a questionnaire;

Response to questionnaires can be increased by making questionnaires, letters, and emails more personal, and preferably kept short;

Response to questionnaires can be increased by giving an incentive, for example, a small amount of money, or a non-monetary incentive such as a pen.

Why is response to questionnaires important?

Postal and electronic questionnaires are a relatively inexpensive way to collect information from people for research purposes. If people do not reply (so called ’non-responders’), the research results will tend to be less accurate.

What did we want to find out?

We wanted to find effective ways to increase response to postal and electronic questionnaires.

What did we do?
We searched for studies that examined any way of increasing questionnaire response.

We summarised the results of the studies.

What did we find?

A very large amount of research has been done to try to identify ways to increase response, and we have included 758 studies in this Cochrane methodology review update. The studies included a wide range of people asked to complete a questionnaire, from patients, doctors, university students, and professors, to marketing managers, accountants, and grocery store managers.

We found that response will be increased by contacting people before they are sent a questionnaire. We also found that response to postal questionnaires will be increased if they are sent by a university. Response can also be increased by giving an incentive, for example, a small amount of money, or a non-monetary incentive such as a pen. Response may be higher using a postal questionnaire rather than an electronic one, or by providing a choice of response modes (electronic or postal). Response can be increased by making questionnaires, letters, and emails more personal, and preferably kept short.

What are the limitations of the evidence?

We had to exclude some studies because we could not confirm that they were free from bias.

How up-to-date is this evidence?

This review updates our previous review. The evidence is up-to-date to December 2021.