The Census Bureau released its new American Community Survey data the other day. Three year averages for a variety of socio-economic variables are now available for all geographic areas that have at least 20,000 people. The ACS has been releasing annual data for most of this decade for areas with at least 65,000 people and will continue to do so. They didn’t provide data for smaller areas because the numbers were not as statistically robust. Now that they have three years of data, they can average the numbers for three years and get sound data for areas with a population of at least 20k.
Data for 2005 to 2007 is available now, and like the annual numbers, you’ll get a range of values and a confidence interval. For example, we can say with 90% confidence that the estimated population of Atlantic City, NJ between 2005 and 2007 was 35,770, plus or minus 1,749 people. The Bureau created this estimate based on a sample of 1,379 people in AC.
Next year, the census will release new annual numbers for areas with a population of at least 65k, and will update the three year averages for areas with 20k by adding the newest year of data and dropping the oldest one to calculate a new average.
All of the data is available through the American Factfinder.
If you are looking for population figures for basic indicators (population, race, gender, age, and housing units) for basic geographic areas (states, counties, places, and metro areas), you’ll probably want to consider using estimates from the Bureau’s Population Estimates program instead. Their annual estimates are based on a demographic calculation that factors in births, deaths, and migration, and is not based on a survey (according to that program, Atlantic City had 39,684 residents in 2007 – 4,090 more people than the ACS midrange estimate). If you’re looking for any other kind of data (ethnicity, immigration status, income, poverty, rent, home value, etc) the ACS is your best bet.
By 2010 the Bureau will begin releasing ACS 5 year avearges for all geographic areas. Of course, we’ll also have our next decennial census in 2010. The big change here is that, since we’ll have the ACS churning out data for all areas for every year from that point forward, the Bureau is doing away with the long form (which was sent to one in six households) that was issued in past censuses, and will only collect data using the basic short form, which gets distributed to everyone. For more info on this change, see the Bureau’s Census 2010 info page.