Davis et al. (1995) estimated the number of uninsured adults age 18 to 64 using the 1993 Kaiser/Commonwealth Survey of Americans. The survey consisted of telephone interviews with a nationally representative sample of 2,000 adults in August 1993. Davis et al. found that one-third of all adults, or 53 million adults, lacked health insurance at some point during the 2-year period from 1991 to 1993. They also found that at the time of the survey in August 1993, 18 percent of all adults were uninsured, which is very close to EBRI's estimate, based on the CPS, that 19 percent of adults age 18 to 64 in 1993 were uninsured (Fronstin 1995). The survey had a response rate of only 53 percent (compared with CPS and SIPP response rates in excess of 90 percent) raising concern about potential response bias. The possible effect of Medicaid underreporting on these findings is unknown because the percentage of respondents with Medicaid was not reported.