The importance of survey comparability

The US Census Bureau is reportedly overhauling the questionnaire and methodology of its annual survey on health insurance, possibly making old and new data incomparable. Moreover, the changes might make it virtually impossible to assess the impact of the Obama administration's new Affordable Care Act (link):

With the new questions, “it is likely that the Census Bureau will decide that there is a break in series for the health insurance estimates,” says another agency document describing the changes. This “break in trend” will complicate efforts to trace the impact of the Affordable Care Act, it said.

Survey comparability is incidentally an issue that beleaguers our own statistical system, especially where poverty and unemployment data are concerned. While survey updates are usually justified as an effort to adhere to international standards and best practices, there is a case for conducting the same survey using old methods if only to retain the comparability of data over time, especially for purposes of policy analysis and reforms.