asdc annual meeting carolyn trent, socioeconomic analyst center for business and economic research...
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C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Population Estimates and Projections
ASDC Annual Meeting
Carolyn Trent, Socioeconomic AnalystCenter for Business and Economic Research
November 10, 2011
Culverhouse College of Commerce and Business Administration
The University of Alabama
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Measuring the population
Census of Population: Actual enumeration of the population of an area on a given date.
Population Estimate: Calculated population of an area on a date which has already passed.
Population Projection: Calculation of what the population of an area may be at a specified future date(s).
Note: An estimate or projection is generally more reliable the larger the
population being determined and the less detail required.
Culverhouse College of Commerce and Business Administration, The University of Alabama 2
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Census of Population
Census 2010 counted population, collecting Age, sex, race, ethnicity
Household size and composition, type of unit, ownership
Separately enumerated group quarters
Sources of error:− Some people likely not counted (mail participation rates:
Alabama 72%, United States 74%; others counted in follow-up activities)
− People may not accurately report their age, race, ethnicity
All other socioeconomic data now from ACS
Culverhouse College of Commerce and Business Administration, The University of Alabama 3
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Center for Business and Economic Research, The University of Alabama 4
Alabama Population, 1950-2010
2000-2010 Gain: Alabama 7.5% U.S. 9.7%
Change fromCensus Previous CensusApril 1 Number Percent
1950 3,061,743
1960 3,266,740 204,997 6.7
1970 3,444,165 177,425 5.4
1980 3,893,888 449,723 13.1
1990 4,040,587 146,699 3.8
2000 4,447,100 406,513 10.1
2010 4,779,736 332,636 7.5
Source: U.S. Census Bureau.
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Population Estimates
Alabama uses the Census Bureau’s annual population estimates. CBER supplies data for these estimates through the FSCPE.
Census estimates:Calculated as of July 1 each year
Produced at the state, county, subcounty levels
Used as controls for ACS data
County series uses administrative records data; state is calculated as sum of counties
Subcounty estimates (places, balance of county) look at housing unit change
Entire series is recalculated each year
Reviewed by CBER/ASDC before finalized and releasedCulverhouse College of Commerce and Business Administration, The University of Alabama 5
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Census Bureau Population Estimates Schedule
Note: All releases below are July 1, 2011 estimates.
U.S. and state population and components of change 12/11
County population and components of change 04/12
Metropolitan and micro area population 04/12
State population by age/sex 05/12
State/county population by age/sex/race/Hispanic origin 05/12
Place/county subdivision population 06/12
State and county housing unit estimates 06/12
Culverhouse College of Commerce and Business Administration, The University of Alabama 6
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
State/County Estimates
Based on administrative recordsBirths and deaths annually from FSCPE and NCHS
Net domestic migration under 65 population from federal income tax returns, military movements
Net domestic migration 65+ from Medicare enrollees
Net international migration from ACS, Census, other sources
Group Quarters Begin with Census count of GQs by county
Census data by type of GQ, but we don’t have a list of GQs that were counted
Annual updates of GQ populations sent in by CBER (FSCPE). Also report new GQs.
Culverhouse College of Commerce and Business Administration, The University of Alabama 7
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Subcounty/Housing Unit Estimates
Housing units estimated annually for every county and subcounty geography
Begin with Census 2010 base
Add estimate of new construction in prior year, using Census Bureau building permit data. Assume 6-month lag from permit date to completion.
For areas without permits, estimate non-permitted construction from annual Survey of Construction (SOC)
Add new mobile home placements
Subtract estimate of housing loss using percentages derived from 1999-2007 American Housing Survey (AHS)
Use these housing unit estimates to distribute county estimate totals to subcounty geographies
Used as controls for ACS housing units
Culverhouse College of Commerce and Business Administration, The University of Alabama 8
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Postcensal vs Intercensal Estimates
Postcensal estimates—for decade following a census
Build on Census 2010 count, modified by differences from boundary changes to create estimates base
New vintage every year replaces prior years
Intercensal estimates—estimates for 2000 to 2009 were recalculated to end up at the Census 2010 count.
Alabama’s July 1, 2009 postcensal estimate was too low:
Postcensal 4,708,708 Intercensal 4,757,938
Difference of 49,230 (1.0 percent) Culverhouse College of Commerce and Business Administration, The University of Alabama 9
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Challenges to Estimates
Localities are given the opportunity to challenge their population estimates.
Challenges usually based on housing unit counts
Challenge process suspended early in 2010; will resume when the July 1, 2011 estimates are released
Census Bureau is reevaluating the challenge process and will issue new guidelines
In the past, most challenges were approved, but not likely to be the case in the future
For places that had challenges accepted during the past decade, Census Bureau analysis showed that the 2010 original population estimate tended to be closer to the 2010 Census result than the estimate with the challenge
During the past decade, 6 Alabama cities and towns won challenges, for a combined total of 3,913 residents added
Culverhouse College of Commerce and Business Administration, The University of Alabama 10
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
How do disruptions affect estimates?
April 27 tornadoesTax returns were sent in by April 18, 2011. So IRS address changes resulting from the destruction won’t show up until 2012—when people may have already moved back or again. The July 1, 2011 population estimate likely won’t be correct for hard hit areas.
Additional data was collected to calculate population estimates after Hurricane Katrina for impacted areas.
New immigration lawPush to count Hispanics in Census 2010—legal or illegal
From that base count, how do we assess outmigration in response to the law?
Also problem for population projectionsCulverhouse College of Commerce and Business Administration, The University of Alabama 11
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Population Projections
Prepared by the Center for Business and Economic Research for over 40 years.
Utilize a cohort component model of the form:
Pop(new) = pop(old) + births – deaths
+ in-migration – out-migration
Calculated for the state and counties for 5-year age groups from 0-4 to 80-84 and 85+, for males/females, races white/black and other.
Currently working on new projections based on Census 2010—will be available in the Spring.
Culverhouse College of Commerce and Business Administration, The University of Alabama 12
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Projections data inputs
For the state and each county, the following are compiled:
Population by age/race/sex for 2000 and 2010
Total number of births by race of mother and sex of child for 2000 through 2010 (from Alabama Center for Health Statistics)
Total number of deaths by race, sex, and age group for 2000 through 2010 (from ACHS)
Census 2010 group quarters population
Culverhouse College of Commerce and Business Administration, The University of Alabama 13
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Projections data calculations
From the data above, CBER calculates for the state and counties:
Total fertility rate by race for women aged 15 to 44 in 2010
Percent of all births for 2000 to 2010 that were male and female
Death rates by age group/race/sex for 2010
Percentage of total 2010 population in group quarters. For counties with large GQ populations, an estimate of that population by age group/race/sex will be subtracted before running the projections and then added back in.
Culverhouse College of Commerce and Business Administration, The University of Alabama 14
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Further data modifications
The dataset created for each geography is examined to see if rates are reasonable and modified as needed:
If large college/university population, birth rate may be dampened as college students are less likely to have children
For small counties, there may not be enough individuals in a particular age/race/sex group and death rates for that group may be substituted from a larger group
Using national life tables, death rates for every geography are modified in each five-year interval to reflect changes in expected mortality and life span.
Culverhouse College of Commerce and Business Administration, The University of Alabama 15
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Producing Projections
The cohort-component program is run separately for the state and each county.
The cohort aspect of the projection process is that the population in each 5-year age group is aged over the 10-year intercensal period—i.e., individuals who were 20-24 in 2000 will be 30-34 in 2010.
The unknown part of the projection is migration rates, which are derived as the residual of the change from 2000 to 2010 after adding births to the 2000 base population and subtracting deaths.
Migration rates are dampened for each 5-year projection period under the assumption that the rate of people leaving a county will slow over time as will the rate of individuals moving in.
County results were adjusted to sum to the state total, although we may change to summing counties to create state total.
Culverhouse College of Commerce and Business Administration, The University of Alabama 16
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
How did CBER do last decade?
Sources of error for projections:Trends may change in ways that weren’t expected
Changes in institutional populations can’t be predicted
Economic development and economy in general affect migration
In projections for 2010 done right after the 2000 Census, CBER was a little too high for Alabama:
Census 2010 4,779,736
CBER 2010 projection 4,838,812
Difference 59,073 (1.2 percent)
Projections are rerun periodically during the decade, taking into account more recent estimates totals
Most recent series controls state and county 2010 totals to Census 2010, but is driven by 1990 to 2000 trends
Culverhouse College of Commerce and Business Administration, The University of Alabama 17
C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Small area population projections
CBER can calculate population projections for areas down to the block group level. These are done on a contract basis.
Change between the two most recent censuses is used as a starting point.
A variety of other information, including building permits, infrastructure development, and recent or upcoming economic development are collected for the geographies to be projected.
ACS data, such as age of housing stock and income levels, is also used. Land area and housing density are examined.
CBER small area projections have been used for regional transportation plans and in socioeconomic impact studies for highway projects.
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C E N T E R F O R B U S I N E S S A N D E C O N O M I C R E S E A R C H
Check CBER website for data
Projections are posted to CBER website
http://cber.cba.ua.edu
under Data, Maps, and Presentations
When new series of projections is complete, summary Excel files will be available there
Detailed age/race/sex projections will not be posted due to their size, but will be available on CD from CBER for purchase
Look for these in March 2012
Thank you!Culverhouse College of Commerce and Business Administration, The University of Alabama 19