Sample and Data Collection
The data collection was prepared during the face-to-face interviews we held with the elderly respondents in 1992. We asked them at the time whether they were willing to take part in this study. If that was the case, we asked them to provide the full names and addresses of a number of people in their network. These data were entered by the interviewer in the computer. When the data was presented to the people in charge of the study, all the information was checked. Typing errors were corrected, and the postal codes often had to be looked up. Then the questionnaires were drawn up. Each questionnaire is different, since each one contains the names of the various other people in the network. Checking the names and addresses was very time-consuming, as was producing the questionnaires (ever since April 1992, a printer has been producing them virtually day and night), and there was usually a period of a few months between the face-to-face interview and the moment when the questionnaires were sent out. In February 1993 we were finished sending out the questionnaires for the first observation (observation G). In May 1993 the second observation (H) began, and the third observation (I) started in June 1994 and finished in April 1995.
Respondents of the Main Survey
In 1992, face-to-face interviews were conducted with 4,494 respondents. In the Network Study, we confined ourselves to the 4,059 respondents who provided information about their relational network.
Questionnaire of the Main Survey
The networks of persons with whom the respondents maintained an important and frequent relationship were stipulated in the Main Study (Van Tilburg, 1995) by using a procedure based upon Cochran et al. (1990) (see LSNa047). The following seven categories were distinguished: people who live in the same household, children and children-in-law, other relatives, neighbors, people one is working or studying with, contacts in organizations, and other contacts (friends and acquaintances). In each of these categories, the respondents were asked to name people above the age of eighteen with whom they had important and regular contact. The size of the network was determined by the number of people who were named in the seven various categories.
A selected number of respondents (N= 1,547) were asked whether they were willing to provide the names and addresses of a maximum of eight of their network members (see LSNa055
). The sample was to a certain extent stratified and consisted of more younger than older respondents, more unmarried, divorced and widowed respondents than respondents with a partner and respondents living in institutions, and more respondents with a low than a high ADL capacity. We asked: "As you know, this study focuses on the living situation and social ties of older adults. We have already asked you a number of questions about your situation, and more questions will follow. However, in order to obtain a more complete picture of your living situation and social ties, we would like to also put a number of questions to some of the people you just mentioned. More specifically, the following individuals: .. We would like to ask them about the composition of their families and about their daily activities. We would also like to ask a number of questions about their social ties. Our intention is to send them a questionnaire they can fill in at home. It takes less than 30 minutes to do so. Naturally, as is the case with the answers you have given, the information they provide will be treated confidentially, and will not be passed on to third parties. You will receive a questionnaire with roughly the same questions at the same time as they are approached. That questionnaire contains a number of questions that are different from the ones I am asking you today, and gives you an opportunity to be fully informed about what the next steps will be in this study. In the letter accompanying the questionnaire, we will mention that you have made it possible for us to contact them. Of course, it is up to them to decide for themselves whether or not they wish to respond. At this point I would like to ask you: Are you willing to participate in this part of the study? (Choice of answers: no; yes, under conditions; yes, no conditions).
The network members that were approached in the Network Study were the eight with the highest frequency of contact. If unconditional permission for all the addresses was obtained, the complete names and address of each selected network member were recorded. Otherwise, permission to obtain the name and address was requested for each selected network member separately. As a result of this procedure, 812 respondents refused to give permission to approach their network members, 326 respondents gave unconditional permission, and the others gave permission under the condition that only particular network members would be approached or said they would have to ask the network members' permission individually. Furthermore, to be prepared for the Network Study, we wanted to know about which relationships between network members questions could be posed in the network questionnaire, and asked questions on the density of the network (see LSNa056
): "Can you tell me which of these .. people are regularly in touch with one another without any involvement on your part? I will list pairs of names. You will notice, however, that not all the names will be listed. People who are related to each other are apt to keep in touch regularly without any involvement on your part. Is .. regularly in touch with ..?"
After this part of the questionnaire, the respondents were asked (see LSNa047) about the structural properties of the relationships or the network members (e.g. age, travel time, marital status, employment status) and about instrumental and emotional support received and given. Questions were posed only for the twelve or less relationships with the highest frequency of contact.
Respondents of the Network Study
After the data in the Main Study were received from the interviewers, the names and addresses of the network members mentioned were read from the diskettes, cleaned and stored in a database. If necessary, the respondents in the Main Study (anchors) were approached to ask whether they had received permission from their network members. Via this procedure, or by another report on the part of the anchors, 64 anchors refused to cooperate and 2 anchors who had refused at the time of the face-to-face interview said they were now willing to cooperate in the Network Study. This meant there were 673 anchors available for the Network Study. Besides these anchors, a selection of their network members served as respondents. The questionnaires were mailed between 15 and 349 days after the face-to-face interview (median 115 days), starting in April 1992. There were several reasons for the delay between the face-to-face interview and the mailing of the questionnaires, the most important of which was that the cleaning of the addresses, the second approach of the anchors by telephone or letter if more information was necessary, and the printing of the questionnaires were very time-consuming.