Respondents of a follow-up web-based survey

Background: The use of web-based surveys has increased in recent years, due to an increase in internet access and lower cost. However, studies have found disproportional response to web surveys from male, younger, and better educated adults. Household internet access is higher in Santa Clara County (SCC), California, located in Silicon Valley, than the national figure (87% versus 73%). We conducted a web-based follow-up survey to a random-digit-dial (RDD) telephone survey in SCC, to assess whether demographic biases between web and RDD telephone respondents were still evident in an area with high internet access.

Methods: Data are from a survey of adults conducted in 2013-14. The web component was sent to eligible telephone survey respondents (completed the phone survey in English, reported recent internet use, agreed to be re-contacted, and provided a valid email address). Both surveys were conducted by Westat, a research firm headquartered in Rockville, MD. Among 4,186 telephone respondents, 1,176 were eligible and invited to take the web survey (web survey response rate = 41.0%). We compared characteristics of respondents eligible for and completing the web survey (N=482), relative to the telephone survey.

Results: Relative to telephone survey respondents, those eligible for the web survey were more likely to be male (47% versus 41%); non-Hispanic White (67% versus 58%), college graduates (68% versus 45%), have household incomes of $75,000 or more (57% versus 45%), US born (73% versus 65%), and younger (mean age, 55 versus 59). Web respondents did not differ substantially by gender from telephone respondents (43% versus 41% for males), but were even more likely to be White (82% versus 58%), college graduates (75% versus 45%), have household incomes of incomes of $75,000 or more (66% versus 45%), and US born (84% versus 65%). Unlike for eligibility, the mean age was similar (both age 59).

Conclusion: Unlike previous studies, we found that web survey respondents in an area with high internet access were only slightly more likely to be male but they were of similar age to RDD telephone survey respondents, even though these groups were more likely to be eligible. However, web survey respondents were more likely to be White, well-educated, higher income, and US born. These biases were even more pronounced for those who completed the web survey versus those who were eligible.