Methodology for calculating city percentages of county hardest-to-count The California Hard-to-Count (CA-HTC) Index is based on census tract-level data. Census tracts don’t cross county boundaries but they sometimes cross city boundaries. As a result, there is no simple way to calculate 482 cities’ percentages of counties’ hardest-to-count populations. These are estimated percentages. The approach used is based on combining 2010 census block geography with 2016 city boundaries, using geographic information system software (GIS). The goal is to capture changes in city boundaries since 2010, as well as several incorporations since then. Population at the block level is available only from the decennial census, the most recent of which is 2010. Population growth in blocks within hardest-to-count tracts wouldn’t be reflected. Based on the methodology above, the city of Los Angeles had a 2010 population of 2,085,282 in the county’s hardest-to-count census tracts. Those tracts had a 2010 population of 4,015,691, which is 51.9 percent.