**Haystaq Projection Methodology **
STEP 1 Aggregate 2010 Census Block data to the Block Group level. Update the 2018 ACS 5-year estimates at the state level to match the Census Population Estimates for 2018. Use the updated 2018 ACS 5-year estimates to calculate a rate of change at the Block Group level. Calculate this rate of change for total population, as well as for every race category and hispanic origin category, so as not to assume a standard rate of change across race categories.

STEP 2 Use geocoded voter file and commercial file data to identify areas of new development areas that are now inhabited that were previously unpopulated in the 2010 Census. Calculate the rate of change for total population, and race and hispanic origin categories, at the county level for the counties that have areas of new development, excluding the Block Groups with new development. We found that by using the county rate of change for these areas, we can estimate a rate of change that is more stable and geographically accurate than a Block Group level average for the area, for example.

STEP 3 Update 2010 Census Block Group data using the calculated rates of change from STEP 1, for areas that are not new developments. For new developments, update the 2010 Census Block Group data using the county-level rates of change calculated in STEP 2.

STEP 4 Disaggregate population projections at the Block Group level to the Block level. Use the commercial file data to find the Block to Block Group population proportions, as this data is from 2020. For Block Groups that contain Blocks that do not have population on the 2020 commercial file, use the 2010 Census Block to Block Group proportions to disaggregate the Block Group level projections.

STEP 5 Use the Largest Remainder Method to round the population projections for the race and hispanic origin categories to sum to the total projected population at the Block and Block Group levels.