This age group has had a low response rate and a greater dropout bias over time than other age groups in the survey. The purpose of the experiment was to investigate whether alternative response modes and contact strategies could provide higher participation and better representativeness, and whether a combination of web and paper surveys would produce measurement differences that affect the results. The experiment included a random sample of 5,172 persons aged 80 and older, drawn from the Norwegian Population Register. After removing persons who have died or emigrated, the gross sample consisted of 4,996 persons. The participants were randomly assigned to 12 experimental groups. The groups differed from each other by response mode (web or paper) and contact strategy (digital letter in Altinn, letter by post and telephone recruitment), and by whether digital contact information from the Norwegian Contact and Reservation Register (KRR) could be used or not. The overall response rate in the experiment was 25.1 percent, but varied greatly between the groups: from 1.7 percent in the group that could not be contacted digitally and who received a letter by postal mail and were supposed to respond online, to 58.1 percent in the group that is digitally contactable who received a paper survey and was contacted by telephone, digitally in Altinn and by postal mail.
The analyses show that paper surveys give a clearly higher response rate than web surveys among people 80 years of age and older. This applies especially to people who are not digitally contactable, but also among those who can be contacted digitally. Paper surveys also provide a net sample that is closer to the gross sample in terms of age, gender and several socio-demographic characteristics. Respondents who respond on paper include to a greater extent the very oldest, more women, more people living alone and more people with low education and low income. The analyses also indicate that paper surveys reach older people with poorer health and less social contact to a greater extent.
Telephone recruitment and postal mail appear to enhance participation, especially when these contact strategies are combined with paper surveys as response mode. In contrast, telephone recruitment alone provides little benefit when respondents still must respond to a web survey without the support of a physical letter received by postal mail. A main finding is therefore that higher response rates among the oldest are not primarily achieved through more digital reminders, but by reducing the digital thresholds for participation. This is particularly true for people who cannot be contacted digitally.
When it comes to measurement differences, the analyses find only small differences between web and paper for most question types. However, systematic differences have been demonstrated in questions about subjective quality of life with longer response scales. Respondents on paper respond somewhat more positively here than respondents on the web. The analyses suggest that this is largely due to different visual presentations of these longer response scales in the two modes. If web and paper are to be combined in future surveys, the forms should therefore be designed as similarly as possible, especially for questions with long response scales.
Overall, the experiment shows that it is possible to achieve both a higher response rate and better representativeness among people 80 years of age and older by offering paper surveys and using several high quality contact strategies. The results also suggest that better representation provides a more comprehensive picture of the health, social contact and quality of life of older people. The recommendations based on the findings are that paper surveys should be considered for selected groups with weak digital capabilities, and that further development of the Quality of Life Survey emphasizes both representativeness, costs and good harmonization between response modes.