Social Explorer’s Andrew Beveridge explains where detailed demographic data comes from in his latest Gotham Gazette column “Under a New Name, Census Data Stands Ready for Perusal.”

The 2010 census has been rolling out since February with New York state getting the first of its data on March 24 and more data releases during the summer. Yet, almost every day reporters, redistricting specialists and even other demographers ask when data to answer questions such as the following will be released:

• When will we know the number of immigrants in New York City and in various neighborhoods throughout the city?
• How many Hispanic citizens of voting age live in Washington Heights?
• Has the median income in Jackson Heights grown or declined since 2000?
• How many veterans from the Iraq and Afghanistan wars live in Staten Island? In the Bronx? On the Upper West Side?
• Which recent college graduates are ending up with jobs? How much do they make? How many are living at home with their parents?
• Has the number of people working in finance increased?

The answer is simple and surprising: “All the information you need was already released on Dec. 14 last year.”

As you may recall, the census form you filled out last spring had just a few basic questions. So the data released on the basis of that can only include: number of people, dwelling owned with or without a mortgage or rented with or without cash rent, relationship to householder, sex, age, and race or races, including principal tribe or group, if Native-American, Asian or Pacific Islander. The other data — indeed the data that in many ways is the most interesting and heavily used — comes from the American Community Survey, or ACS, which is actually “the rest of the census” and was released in December.

Beveridge writes about the development, content and frequency of the ACS, and the differences between it and the old Census long form, which it replaced.

Beginning in 2005, the Census Bureau began to collect data for the American Community Survey, which is very similar to the old long form. That survey gets responses from about 2 million households and residents of group quarters (prison, dormitory, institution) every year, and tracks the same sort of data that was produced by the long form sample. The survey takes place all year and interviews, where necessary, are conducted by permanent staff — not the temporary workers who interview for decennial census.

Data from the annual survey are released in one-year, three-year and five-year files (with increasing levels of detail).  The multi-year files offer the most detailed data, but also cover the longest period of time.  For instance the five-year file includes data both before and after the financial crisis of ‘07-’08.

Beveridge also discusses flaws with the Census Bureau’s handling of sampling errors (resulting in potentially negative population counts) and the bureau’s policies on suppressing certain data.  A memo Beveridge wrote to the Census Bureau on the topic of their estimation of confidence intervals and its misuse, along with the agency’s response is available here.

Though not as well known as the Decennial Census, the ACS offers a wealth of demographic information and is available right now.

In sum, despite some differences between the American Community Survey and the old census long form data, the survey is in most ways superior. Not only is the data released more often and in a more timely fashion, but the numbers may be more accurate since the survey is conducted by a permanent interview staff. So the next time you cannot find the data you want in the census report look for it in the American Community Survey.

Click here for the full column. Social Explorer subscribers can access ACS data anytime through maps and reports.