Previous studies reveal that, using solely U.S. census data, over 60 % population could be uniquely identified with (gender, zip code, date of birth) in 1990 and 2000. This paper extends these studies to examine spatial variation of uniqueness in 2010. We provide (1) the comparison of national level uniqueness between 2000 and 2010, and (2) the investigation of spatial variation of uniqueness in different regions and at different scales. The comparison between 2000 and 2010 reveals that, although overall uniqueness changes little, the uniqueness of middle-age group has significantly decreased. Spatial variation studies show that similar characteristics in age-group uniqueness exist in different regions. Finally, the analysis at different scales discloses that overall uniqueness decreases, and the difference between age-group uniqueness reduce, when geographical scales focus on the cores of urban area. This study offers contributions to geographic information privacy, particularly relevant to reverse geocoding and related spatial aggregation techniques.