Recently, the State Demographer’s office released population projections for 2010 through 2030. We did a press release for that and the document can be found by clicking here. Some stories have sounded like the projection for 2010 is the estimate for 2010. That is not the case and this blog is being written to clarify the difference between the these two terms – estimates and projections. There will be a lot of information about 2010 coming out n the coming months. Here is a summary of the key products and their differences.
THE 2010 SHORT FORM CENSUS OR DECENNIAL CENSUS
An analogy for the Census is the inventory or hard count used in retail stores. The Census is an effort to count everyone at one time at their usual place of residence. It is the official count of the population and is used to apportion the House of Representatives, redistrict congressional and state legislative districts, and is used is various Federal funding formulas. It is used to gauge the accuracy of population estimates.
THE ANNUAL POPULATION ESTIMATES
An estimate is a calculation of the current population based on a set of administrative records or other data that reflect current or recent conditions. Continuing the retail sales analogy, the estimates are like tracking a stores goods through sales and shipping data (administrative records). They may be real time data or there can be a lag. For instance a the shipping invoice is still in accounting and not yet available to the person who is trying to project future sales. Estimates provide information between censuses about how things are changing.
Projections are done to see where past trends seem to be taking us. If there is strong enough belief in them then they become forecasts. They are often based on recent or long term historic data and are analyzed or modeled to see where they are going. A buyer for a retail store is interested in what to order for the coming Christmas season so he looks at historic data to project sales before he invests in certain goods. As the goods start to arrive, he estimates his total sales volume as current information becomes available.
Each of these of these play a role in private and public decision making. We are still gathering data for the estimates and the 2010 estimate will be released later this year or in early 2011.