Assessing Changes in Coverage Bias of Web Surveys in the United States

The rising costs and declining response rates of traditional survey modes have spurred many organizations to conduct surveys online. Less expensive broadband connections and the popularity of smartphones have also made it easier for many to access the Internet. The General Social Survey (GSS) shows that the percentage of American adults who use the Internet increased from 69 percent in 2006 to 86 percent in 2014. The increased access has reduced some concerns about the representativeness of Internet surveys. However, there remains little research into coverage bias, which occurs if those not in the sampling frame differ from the target population on variables of interest. This raises a question: With the increase in Internet access, has there been any change in the coverage bias of web surveys? To assess coverage bias, we analyze the GSS to determine whether those with Internet access and those without it became more or less similar between 2006 and 2014. We calculate the potential coverage bias of web-only surveys over these years for sex, age, education, income, race, political ideology, urbanicity, and life satisfaction. We also compare the bias observed in the United States to that in Europe. Our results illustrate that relative coverage bias associated with education, income, race, and age declined between 2006 and 2014, but bias still exists.