title: The adequacy of household survey data for evaluating the nongroup health insurance market.
abstract: OBJECTIVE
  To evaluate the accuracy of household survey estimates of the size and composition of the nonelderly population covered by nongroup health insurance.
  
  
  METHODS
  Health insurance enrollment statistics reported to New Jersey insurance regulators. Household data from the following sources: the 2002 Current Population Survey (CPS)-March Demographic Supplement, the 1997 and 1999 National Surveys of America's Families (NSAF), the 2001 New Jersey Family Health Survey (NJFHS), a 2002 survey of known nongroup health insurance enrollees, a small 2004 survey testing alternative health insurance question wording.
  
  
  METHODS
  To assess the extent of bias in estimates of the size of the nongroup health insurance market in New Jersey, enrollment trends are compared between official enrollment statistics reported by insurance carriers to state insurance regulators with estimates from three general population household surveys. Next, to evaluate possible bias in the demographic and socioeconomic composition of the New Jersey nongroup market, distributions of characteristics of the enrolled population are contrasted among general household surveys and a survey of known nongroup subscribers. Finally, based on inferences drawn from these comparisons, alternative health insurance question wording was developed and tested in a local survey to test the potential for misreporting enrollment in nongroup coverage in a low-income population.
  
  
  METHODS
  Data for nonelderly New Jersey residents from the 2002 CPS (n=5,028) and the 1997 and 1999 NSAF (n=6,467 and 7,272, respectively) were obtained from public sources. The 2001 NJFHS (n=5,580 nonelderly) was conducted for a sample drawn by random digit dialing and employed computer-assisted telephone interviews and trained, professional interviewers. Sampling weights are used to adjust for under-coverage of households without telephones and other factors. In addition, a modified version of the NJFHS was administered to a 2002 sample of known nongroup subscribers (n=1,398) using the same field methods. These lists were provided by four of the five largest New Jersey nongroup insurance carriers, which represented 95 percent of all nongroup enrollees in the state. Finally, a modified version of the NJFHS questionnaire was fielded using similar methods as part of a local health survey in New Brunswick, New Jersey, in 2004 (n=1,460 nonelderly).
  
  
  RESULTS
  General household sample surveys, including the widely used CPS, yield substantially higher estimates of nongroup enrollment compared with administrative totals and yield estimates of the characteristics of the nongroup population that vary greatly from a survey of known nongroup subscribers. A small survey testing a question about source of payment for direct-purchased coverage suggests than many public coverage enrollees report nongroup coverage.
  
  
  CONCLUSIONS
  Nongroup health insurance has been subject to more than a decade of reform and is of continuing policy interest. Comparisons of unique data from a survey of known nongroup subscribers and administrative sources to household surveys strongly suggest that the latter overstates the number and misrepresent the composition of the nongroup population. Research on the nongroup market using available sources should be interpreted cautiously and survey methods should be reexamined.
authors.affiliation: Center for State Health Policy, Rutgers University, 55 Commercial Avenue, 3rd Floor, New Brunswick, NJ 08901, USA.
authors.forename: Joel C
authors.initials: JC
authors.lastname: Cantor
authors.forename: Alan C
authors.initials: AC
authors.lastname: Monheit
authors.forename: Susan
authors.initials: S
authors.lastname: Brownlee
authors.forename: Carl
authors.initials: C
authors.lastname: Schneider
mesh_terms: D000293:Adolescent; D000328:Adult; D015982:Bias; D003625:Data Collection / Q000379:methods*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D019458:Insurance Coverage / Q000706:statistics & numerical data*; D007348:Insurance, Health / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009515:New Jersey; D012959:Socioeconomic Factors; D013221:State Health Plans / Q000458:organization & administration; D014481:United States