1. In Table R1 and W1, Total Workers include Civilian Employed and those working in the Armed Forces. Compared with Workers at Work, Total Workers include workers in strike, vacation and sick etc.
2. In Table R2.C, R5, R7 and R8, Public Transportation includes: Bus or trolley bus, Streetcar or trolley car, Subway or elevated, Railroad, and Ferryboat.
3. In Table W1, Mean Travel Time to Work does not include workers working at home. Average Vehicle Occupancy is calculated by dividing aggregate number of vehicles used in commuting by workers driving alone and carpooling. Average Carpool Size is calculated by dividing aggregate number of vehicles used for carpool by workers carpooling.
4. If numbers or percents cannot be calculated, “— “ is used instead.
5. Margin of Error (MOE): Because the sample size of the American Community Survey is much smaller than the decennial census “long form,” it is more important to understand the potential errors in the tabulated results. Calculation of Standard errors for some of the data elements on these profiles will be based on the Census Bureau method detailed at http://www.census.gov/acs/www/Downloads/ACSGeneralHandbook.pdf. These have been expressed on the profile sheets as “Margins of Error” either as a +/- of a count, or of a percentage, using a 90 percent confidence interval.
6. For large cities, data are based on the definition that existed during the year the data was published. For 2000 data, they are the 2000 definition of the cities, for 2005-2007 data they are based on the 2007 definition.
7. For the total persons, persons in Group Quarter and persons in Households, MOEs for the State and County levels are not calculable because they are controlled through the County estimates program.
8. In R1 and R5, to calculate the MOE for mean value would require a lot of programming so we decided not to do it. For those who are interested in calculating these MOEs themselves, please refer to Example 7 on pages 8-14 and 8-15 of the SF3 document http://www.census.gov/prod/cen2000/doc/sf3.pdf and it shows how to calculate the standard error on mean value.
9. The weights for 3-year ACS data are controlled by county and the controls are an average of estimates over the period. For example, the housing unit control used for a given county in the 2005-2007 weighting is equal to the simple average of the 2005, 2006, and 2007 estimates. However, the estimate for any county may be adjusted, and the ACS uses the most recent estimate for any particular year. That is, in 2007, the county estimate for 2005 or 2006 may have changed and this updated number is used in the 2005-2007 ACS. Please refer to the following link for more detailed discussion. http://www.census.gov/acs/www/Downloads/ACS/Accuracy2005-2007ACS3-Year.pdf.
Since there is no “light rail” option in the ACS questionnaire for the Means of Transportation, we are finding that in some cases, e.g. Houston, TX, people are likely choosing “Other” for the light rail. In other cases, e.g. San Diego, where the light rail is called “The Trolley”, this not causing the same problem. For your area, you may need to include the “other” category when attempting to get a transit total.