In the 2008 ACS, there was a higher percentage of persons with Alaska as their state of residence one year prior, than the levels estimated in previous years. Investigation of the relevant cases has shown that a large proportion of these respondents had no additional residence 1 year ago geographic information below the state level (thus not allowing verification of the report of 'Alaska'). The exact source and cause of this change in the estimate has yet to be determined, but investigation is ongoing.