September 27, 2010

What do you mean by “continental U.S.”?

Q. In your descriptions about how you conduct your polls you use the term “continental United States.” Does that mean you include Alaska or not? And since you presumably do not include Hawaii and the other Pacific Islands that are part of the U.S. do you make any effort to adjust your results for these omissions? And what about Puerto Rico and the U.S. Virgin Islands? There are, in fact, techniques for adjusting results in such circumstances that are mathematically acceptable but, if used, such adjustments and the methods should be disclosed.

The definition of “continental United States” that we and most other major survey organizations use includes the 48 contiguous states but not Alaska, Hawaii, Puerto Rico and the other U.S. territories. We do not interview in Hawaii and Alaska for practical reasons, including time differences and cost. Strictly speaking, our results are generalizable to the population of adults who live in our definition of the continental United States. (It should be noted, however, that our surveys cover about 98% of the total population in all 50 states, Puerto Rico and the other areas you mention.) To correct any minor skews introduced by sampling, we adjust (“weight”) our sample to match the Census Bureau estimates of the age, gender, race and educational attainment characteristics of the U.S. adult population. We also adjust the sample for other characteristics, such as household size. You can find more details in the detailed descriptions that accompany every major report that we release. Here, for example, is a link to the methods chapter in our Economy Survey conducted in May.

Rich Morin, Senior Editor, Pew Research Center