The Census Bureau recently issued "Daytime population" estimates using Census 2000 data (See http://www.census.gov/population/www/socdemo/daytime/daytimepop.html). These estimates include: a. Workers who go to work, no matter where they live, and no matter what time they travel to work. b. Residents of an area who are not workers, including everyone who is below 16, and c. Everyone else who is not a worker, including employed people who did not go to work in the reference period. For each Place (i.e. city) and County, a ratio of total workers to resident workers is calculated. So, places with high in-movements of workers are distinguished from places with high out-movements of workers. For example, Washington, D.C. and Bethesda, Maryland, have high in-movements of workers. The Census Bureau recognizes that this is an elementary measure as it doesn't address travel for all trip purposes, only work-related travel. The estimates do not address: Children going to school. Workers who leave for work late in the day and work in the evening Leaving home for other purposes like shopping, social or recreational trips. Special attractors: universities, hospitals, entertainment centers, regional shopping centers. Absenteeism from work (vacation, illness, etc). It assumes that people who are not workers, including all people under age 16, and all retired people without jobs, do not leave their residence place or county. So, it is going to be a low estimate for some places, and high for others. The level of geographic reporting is all states and counties, and selected places (those with either 2,500 resident workers or total workers). Using CTPP 2000, you can do a similar calculation for any other geography (e.g.: Census Tracts or TAZ or CBD) by: Daytime population in any geography = CTPP Table 1-047 (total population) MINUS first column in CTPP Table 1-001 (total workers living in an the area) PLUS first column in CTPP Table 2-001 (total workers working in the area) Why the CB's Daytime Population Estimates will not be exactly the same as results using CTPP 2000: 1. CTPP 2000 values are rounded (4, and then multiples of 5), while the CB's county and place daytime estimates are not rounded. 2. The CTPP 2000 workplace locations are tabulated after "extended workplace allocation" was completed, which assigns work locations using industry, occupation, travel mode and travel time to workers for whom a workplace location was incomplete or missing. The CB's daytime population estimates do not use the extended allocation results. 3. The CB calculation used the 100 percent count as its total population figure. This may be different than the sample count shown in Table 1-047 of CTPP 2000 Part 1, particularly for places (counties should be the same). For the United States as a whole: About 46 percent of all persons were workers who went to work, so they are assigned to their workplace location. About 23 percent of all persons are under age 16, so they are assigned to their home location. About 28 percent of all persons over age 16 were not in the labor force, so they are assigned to their home location. Of these people NOT in the labor force, about 40 percent are over age 65. About 3 percent of all persons over age 16 were unemployed, so they are assigned to their home location. Just be aware of the limitations of these estimates if you plan to use them! Thank you! Elaine Murakami and Nanda Srinivasan