Written by: Alison Fields and Robert Kominski
Have you moved in the last five years? Earlier today, the Census Bureau released a collection of data on rates of migration, or “geographic mobility.” Between 2011 and 2012, 12 percent of people in the country over age 1 moved at least once. This showed that the rate of yearly migration increased, compared with the previous year’s all-time low of 11.6 percent.
The population of the United States is considered highly mobile. Each year, people move from their place of birth or current residence to live somewhere else in their city, county, state or the nation. When and where people move has a huge impact on the local demographics and economies of the places where they used to live and where they live now.
Knowing the number and some details about movers in and out of a place is part of information on the population that helps the federal government plan for emergency services following natural disasters. State and local planners use migration data for population forecasting and deciding where to put new hospitals, libraries and public schools. Private businesses use it to plan for opening new offices and stores for jobs and commerce.
Generally, we measure migration by asking someone if she was living at her current address at some specific point in the past, such as last year, last month or April 1, 2000. Many of our surveys use the period of one year, which is the case with annual data collected as part of the American Community Survey (ACS) and the question in the Current Population Survey, Annual Social and Economic Supplement (CPS). Some of the products released this week use data from these surveys but look at a longer period – asking, “Where did you live five years ago?”
The five-year question first appeared in 1940 as part of the long-form decennial census data collection. It provided migration data that could be cross-tabulated by a large assortment of social, demographic and economic characteristics, and for relatively small pieces of geography. Along with other questions added to the census that year, it helped measure the effects of the Great Depression. A five-year migration question was added to the CPS in 1975 to help provide an idea of patterns of movement for the beginning part of each decade. It now appears in the CPS data collection every five years.
With the implementation of more routine surveys such as the CPS, it became possible to measure migration more frequently, and in 1948, we added the one-year migration question to the March CPS. With the transition of decennial long-form data collection to the ACS in 2005, an annual migration question was added to that survey to take advantage of its larger sample and greater geographic precision. Even shorter-duration data has been collected as part of the Survey of Income and Program Participation (SIPP), where we can identify moves down to the specific month.
Most of the information released today comes from the CPS. We can look back to 1948 and see the number of movers in the United States and the rate at which people are moving.
Although the rate people move reached an all-time low in 2011 and is now increasing, that does not tell us about the volume of the flow. This graph shows that even when the mover rate is low, there are many Americans moving. This movement affects change across the country. The ACS data released today on state-to-state migration flows is how we know where in the country to see the impact of the change, or where people are moving.
We also observe that the longer the period we ask about in the mover question, the greater the likelihood that someone will tell us that he experienced a move. For example, the CPS 2010 one-year rate of migration reported is 12.5 percent, while the 2010 five-year rate from CPS is 35 percent. Alternatively, 35 percent of people responded that they moved at least once in the last five years, but only 12.5 percent said the same for the previous one year.
Each of these sources provides different and valuable complementary data about the migration process, but because of a variety of operational and definitional contexts, also will not provide exactly comparable data or estimates. No one data collection effort provides the answer to every possible question, so we use multiple data opportunities to provide a fuller and more detailed picture of the issue. Collectively, the different information from these statistical products paints a more vivid picture of our nation’s movers.
More detail about the trends in domestic migration in the United States is available in the new set of products released today on the Geographic Mobility Page.