Data released today by the Census Bureau from its American Community Survey (ACS) show that Massachusetts continues to lead the nation when it comes to health insurance coverage. In 2011, the proportion of people in the state who lacked health insurance coverage was 4.3 percent, compared to the U.S. average of 15.1 percent. In other words, 95.7 percent of people in Massachusetts had some form of health coverage in 2011, compared to 84.9 percent nationwide.
- The overall Massachusetts uninsured rate of 4.3 percent in 2011 is not statistically different from the 2010 rate of 4.4 percent.
- While the overall Massachusetts rate was level, the proportion of 18-24 year olds who lack health insurance declined significantly, from 8.7 percent in FY 2010 to 7.5 percent in 2011. The change is likely due to the implementation of a federal health reform provision that allows young adults to stay on a parent's health plan (similar to, but broader than, the Massachusetts law).
- On the national level, the rate of people who lack insurance coverage showed a significant decline, from 15.5 percent to 15.1 percent. The U.S. decline in the rate of people without health insurance comes as many states take the first steps in implementation of federal health reform. Massachusetts also experienced a significant decline in the rate of uninsurance following passage of the 2006 health reform law.
Note on Health Care Data
There are a number of sources for health insurance coverage data, each of which has slightly different characteristics and each of which produces slightly different results. The three main surveys are:
American Community Survey
The American Community Survey (ACS), which is conducted on an ongoing basis, contacts over 3 million households each year and asks questions about a variety of demographic measures, including age, income, employment, health insurance coverage status and type, and racial characteristics. The Census Bureau began conducting the ACS in 2000, and added questions about health insurance coverage in 2008. Because of its large sample size the ACS provides reliable single year data on the state level, as well as other geographical units (e.g., counties) with populations over 65,000, making it a useful source of information when comparing state health insurance coverage rates. However, because health insurance questions have only been asked since 2008 (and the survey methodology was changed in 2009), the ACS data cannot currently be used to analyze historical trends in coverage.
Current Population Survey
The Current Population Survey (CPS) is an ongoing survey that focuses on wages and employment. The CPS also includes an Annual Social and Economic Supplement (ASEC), conducted mainly in March of each year, which includes more detailed questions about income, health insurance, and other demographic measures. The ASEC uses a much smaller sample sizeabout 100,000 addresses across the countrythan the ACS, but it has been conducted over a longer period of time. The survey asks about health coverage in the year preceding each March, and has tended to result in under-reporting of health insurance coverage and thus higher reported rates of uninsurance in the past, although CPS has made some adjustments to account for this problem. The CPS data can be used to look at historical trends on the national level and, with some caution, on the state level (for instance it is generally advisable to pool two or three years of data when looking at state-level numbers).
Massachusetts Health Insurance Survey
The Massachusetts Health Insurance Survey (MHIS) began in 1998 and has been conducted annually since 2006. The survey reaches about 5,000 households in Massachusetts and is usually conducted in the spring of each year. Survey results for 2011 are not yet available. In earlier years the survey appeared to under-report the number of people without health insurance coverage. Changes in the survey's methodology were made in 2008 and data from that and subsequent surveys cannot be compared to earlier survey results.
While each survey has produced slightly different estimates of health insurance coverage, they all tend to show the same general trend. Despite the variation in the MHIS and CPS ASEC results, both show a sharp drop in the number of uninsured people following passage of the Massachusetts health reform law.
Note on Statistical Significance
The ACS data come from surveys of a random sample of households and thus one cannot be certain that the estimate produced by the sample reflects the actual rate for the entire population. Results will vary from one sample to another to a certain extent, depending on sample size and the particular characteristic that is being measured. When comparing two measuresfor instance, the poverty rate in two different years or two different statesit is important to consider how this sampling variability affects the difference between the two measures. If the difference between the two rates would occur due to variability less than 10 times out of 100, then we can say that we have a 90 percent level of confidence that the difference between the two rates reflects a true difference and is not due to this potential variation. In other words, the chance that the difference between the two estimates is simply the result of random chance is less than 10 percent. While different levels of confidence (e.g., 95 or 99 percent) can be used to measure significance, the 90 percent level is typically used when analyzing ACS data, and that is the measure we use here when defining a difference as significant. For more on calculating levels of confidence and testing for significance, see Appendix 4 in the ACS user guide.