3.3 Interview surveys

Population statistics are the main source of demographic information, but they do not always give all the answers that researchers are looking for about population development.

Population statistics may show, for example, that the birth rate is falling, but they will not be able to shed any light on the reasons for this; the only way to find out is to ask people.

An interview survey is based on a questionnaire, which is sent out to be filled in by the people included in the sample. Alternatively, it is possible to conduct personal interviews where the interviewer puts the questions directly to the interviewee.

Interviews are nowadays often conducted over the phone. However a telephone interview is not possible if the survey includes several sensitive questions. In a survey concerning the birth rate, for example, one sensitive issue is the number of abortions.

The interview survey is a good way of obtaining more detailed information about factors relating to population development. It is also a useful instrument for collecting information on people's opinions.

One difficulty with the interview survey is the high cost of implementation. Furthermore, the reliability of interview responses is not even close to the reliability of information derived from population statistics. The development of sampling and interviewing techniques has, however, helped to improve the reliability of interviews.