Facts at a Glance: Income remains stagnant in Massachusetts
- Median household income is a statistical measure indicating the exact middle of the range of all household incomes, such that half of all households have incomes below the median and half have incomes above it. Under the Census Bureau’s methodology, income refers only to before-tax money income and does not include the value of non-cash benefits such as Medicaid or food stamps.
- All dollar amounts in this summary are expressed in constant 2007 dollars. Inflation adjustments are made using the Consumer Price Index for all urban consumers (CPI-U).
- The Census Bureau’s recent data on poverty and incomes derives from two main sources: the Current Population Survey (CPS) and the American Community Survey (ACS). The CPS is the older of the two surveys – dating back to the 1940s – and is therefore a more reliable source for making comparisons over time (though, due to sample size constraints, data must be pooled over two or three years to do so). The CPS is also the official source for national poverty and income data. However, the ACS is based on a larger sample and is thus able to provide information on a state and sub-state basis that does not have to be pooled over multiple years.
- At various points in this analysis we refer to whether or not the difference between two numbers, usually from two years, is statistically significant. Because the CPS and ACS data are based on a survey of a random sample of individuals meant to represent the entire state or nation, one cannot be certain that the estimate produced by the sample is the actual rate for the entire population. For each number they publish, the Census Bureau includes a "margin of error." Statistically we can say that if there is no difference between the most recent data and the year it is being compared to, 90 random samples out of 100 would fall within our margin of error. This is called a 90 percent confidence interval. Therefore, when this report states that the difference between two numbers is not statistically significant, we are saying that our sample falls within the confidence interval.
Staff
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