The Department of Social and Health Services, Research and Data Analysis developed population estimates at the census block level. These estimates were based on data provided by Claritas, Inc. and Office of Financial Management , June 30, 1997. A boundary coverage of the Networks is overlaid on the census block boundary coverage. For census blocks that cross Network boundaries, the population of the Network is estimated by aerial interpolation. For aerial interpolation, we remove water, parks and other areas, which do not contain any significant population and assume that the population is uniformly distributed in the remaining areas of each census block group.
Aerial interpolation is done only for the age groups used in rate calculations.
It is not based on the entire population. If the interpolation process results in fractions of people the denominator is rounded to the nearest whole person. Since block groups are small with respect to the size of networks and since we have removed areas that do not contain any significant population, we believe that the uniform density assumption provides reasonable population estimates for each Network. The denominators for high school graduation and drop out rates and the 4th, 8th and 11th grade protective factors are school enrollment and respondents to a school survey, respectively. These denominators are available at the school district level.