The Census is Just a Number, Right?
Wednesday, April 1st was Census Day, the date which is used as the determining marker for accurately filling out the census. Every 10 years, a headcount is done so that the government can get a comprehensive picture of the population of the United States – called the decennial census. While on the surface it seems like the census output is just a number, this data ultimately impacts many facets of daily life and gets factored into a plethora of transportation-focused tools.
The letter you receive in the mail makes it very clear, saying – “local communities depend on information from the Census Bureau to fund programs that promote the well-being of families and children as well as equal employment opportunities for you and your neighbors.” Of the many programs that promote the well-being of families, transportation programs have seen vast changes in census usage since its inception in 1790. So how do census numbers affect how we get around?
A Look Back in Time
Transportation initiatives weren’t always part of the census. In fact, the 1960 census was the first time any transportation related questions were asked. Questions included place of work, means of transportation to work, and how many automobiles were located at each household. According to Modernizing the U.S. Census, “the principal impetus for adding the question on place of work to the 1960 census was the need for data on commuting interchanges for use as an indicator of economic integration between large cities and their suburbs as part of the criteria for delineating metropolitan statistical areas.”
As the years went on and codifying data became easier, an influx of transportation data became available. By 1980, the census had included questions on carpooling arrangements, number of riders in carpools, travel time to and from work, and whether or not people with disabilities were able to access public transportation. In order to use this data at a local level, “the DOT contracted with the Bureau of the Census to create a series of special tabulations in a transportation planning package. Metropolitan Planning Organizations (MPOs) obtained the data tabulated for their traffic zones on a cost-reimbursable basis.”
By 1990, the thirst for more data had made the decennial census so cumbersome that survey designers believed response rates were in jeopardy. In 2005, the American Community Survey (ACS) was launched, taking the more detailed socio-economical information such as employment status and income away from the decennial census, and putting it into a survey which gets sent to a rotating population throughout the decade. According to a census FAQ sheet, “the Census Bureau selects a random sample of addresses to be included in the ACS. Each address has about a 1-in-480 chance of being selected in a month, and no address should be selected more than once every 5 years.” Mobility lab recently used ACS data to compile a study on How People Travel to Work in Arlington.
How do the ACS and the Decennial Census Interact?
For transportation planning purposes in many respects the ACS is where most of the useful data comes from because of its built in transportation behavior questions, though the decennial census is used in a variety of ways to supplement the more granular travel data captured by the ACS.
The decennial census has the biggest impact on federal transportation funding. Federal funding through Federal Transit Metropolitan Planning Grants, which helps fund “the planning, engineering, design and evaluation of transit projects and other transportation-related studies” in urbanized areas, takes census data into consideration when allocating money. “An urbanized area is an incorporated area with a population of 50,000 or more that is designated as such by the U.S. Department of Commerce, Bureau of the Census.”
Ensuring an accurate population count during the decennial census can be crucial for many areas, as the funding formula differs as the population changes. “For areas of 50,000 to 199,999 in population, the formula is based on population and population density. For areas with populations of 200,000 and more, the formula is based on a combination of bus revenue vehicle miles, bus passenger miles, fixed guideway revenue vehicle miles, and fixed guideway route miles as well as population and population density.” You can review the latest formula on DOT’s website.
Another tool that relies on decennial census data is the Location Affordability Index (LAI), which measures housing and transportation costs at the neighborhood level. The LAI “gives the percentage of a given family’s income estimated to be spent on housing and transportation costs in a given location for eight different household profiles. It is calculated using actual and modeled data for Census block groups in all 942 Combined Base Statistical Areas, which cover 94% of the U.S. population.”
The LAI attempts to show the relationship between housing and transportation costs and can be used in identifying areas where lack of transportation options can lead to a higher cost of living not because of housing, but of transportation itself. This type of insight may lead to better, or more transportation options to make the region more livable for a greater population.
Block-level decennial census data is also used in the OnTheMap tool, part of the Longitudinal Employer-Household Dynamics program, which compiles employment and commuter data to show the flow of employees from region to region. Insights into this type of travel behavior help transportation agencies allocate necessary resources to in-demand areas, much like the LAI.
What’s in A Number?
Ensuring every citizen is counted is a hallmark statement from state, local, and federal officials once every decade. It’s impossible to miss the stream of advertisements and mailers. Countless hours of planning and execution go into obtaining an accurate picture of the United States population. While many agencies at all levels of government, as well as citizens, get to reap the benefits of census data, transportation planners rely on the data to provide reliable, safe, and convenient transportation options for their communities. Think about your commute while you’re filling out the census and know that you’re doing your part to contribute to better transportation and TDM planning- with just a number.