population estimates and projections in the u. s
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Population Estimates and Projections in the U. S. John F. Long www.usademography.com. Population Estimates and Projections. Both Estimates and Projections Calculate the size of the population in the absence of complete demographic data May also calculate demographic characteristics - PowerPoint PPT PresentationTRANSCRIPT
Population Estimates and Population Estimates and Projections in the U. S.Projections in the U. S.
John F. LongJohn F. Long
www.usademography.comwww.usademography.com
Population Estimates and Population Estimates and ProjectionsProjections
Both Estimates and Projections Both Estimates and Projections – Calculate the size of the population in the absence of complete demographic Calculate the size of the population in the absence of complete demographic
datadata– May also calculate demographic characteristicsMay also calculate demographic characteristics– Are used for planning and policy decisionsAre used for planning and policy decisions
Population ProjectionsPopulation Projections– Project trends beyond the time interval of the input dataProject trends beyond the time interval of the input data– Use mathematical models of varying sophisticationUse mathematical models of varying sophistication– Often use models of components of demographic change: births, deaths, Often use models of components of demographic change: births, deaths,
migration, and immigrationmigration, and immigration
Population EstimatesPopulation Estimates– Estimate population using data from the same time periodEstimate population using data from the same time period– May use demographic data: births and deathsMay use demographic data: births and deaths– May use indicator variables – housing, administrative recordsMay use indicator variables – housing, administrative records
Projection: Simple ExtrapolationProjection: Simple Extrapolation
PPx+1x+1
t+1t+1 = (P = (Pxx
tt ) ((P ) ((Pxx
tt )/(P )/(Px-1x-1
t-1t-1))))
where, where,
PPxx
tt is the population age x in a given place at is the population age x in a given place at
time time tt
U.S. Population: Census Counts from U.S. Population: Census Counts from 1790 and Projections for 1860-19301790 and Projections for 1860-1930
Source: U.S Census Bureau, Decennial Censuses 1790-1930 ; Abraham Lincoln, “Annual Message to Congress: December 1, 1862”.
Population Projections UsingPopulation Projections UsingComponents of ChangeComponents of Change
Begins with a measured base population (census, etc)Begins with a measured base population (census, etc) Calculates trends in births, death, migrationCalculates trends in births, death, migration Usually based on cohort-component method Usually based on cohort-component method May used multi-regional projection matrix methodsMay used multi-regional projection matrix methods Accepted method for official U.S. population projectionsAccepted method for official U.S. population projections
Component-based ProjectionsComponent-based Projections
PPx+1x+1
t+1t+1 = P = Pxx
tt + B (if x<0) - D + B (if x<0) - Dxx + I + I
xx - O - O
xx
where, where,
PPxx
tt is the population age x in a given place at time t is the population age x in a given place at time t
B is the number of births in a given place between t and t+1B is the number of births in a given place between t and t+1
DDxx is then number of deaths age x in a given place between t and t+1 is then number of deaths age x in a given place between t and t+1
IIxx is the number of in-migrants age x to a given place between t and t+1 is the number of in-migrants age x to a given place between t and t+1
OOxx is the number of out-migrants age x from a given place between t is the number of out-migrants age x from a given place between t
and t+1.and t+1.
Development of Demographic Development of Demographic Accounting ApproachAccounting Approach
– Nationwide birth and death registration began in the early 1900’sNationwide birth and death registration began in the early 1900’s– Estimates and projections for states, counties, and places Estimates and projections for states, counties, and places
developed in the last half of the 20developed in the last half of the 20thth century century– Demographic Analysis became a key tool to evaluate decennial Demographic Analysis became a key tool to evaluate decennial
census qualitycensus quality– ““Integrated” accounting system implicit in the American Community Integrated” accounting system implicit in the American Community
Survey for the 21Survey for the 21stst century century
Elements of US Demographic Elements of US Demographic Accounting SystemAccounting System
Master Address FilesMaster Address Files Decennial CensusesDecennial Censuses Birth and Death Registers (NCHS)Birth and Death Registers (NCHS) Immigration Data (INS & ACS)Immigration Data (INS & ACS) Domestic Migration Data (IRS)Domestic Migration Data (IRS) Adjustments and CorrectionsAdjustments and Corrections American Community SurveyAmerican Community Survey
Master Address FilesMaster Address Files
Importance of tying population to geographyImportance of tying population to geography Address canvassing prior to census yearAddress canvassing prior to census year Corrections during census operationCorrections during census operation Updates between censusesUpdates between censuses Provides “frame” for census and survey operationsProvides “frame” for census and survey operations Issues with permits, construction, demolitions, and Issues with permits, construction, demolitions, and
conversionsconversions Addresses vs. physical location.Addresses vs. physical location.
Decennial Census CountsDecennial Census Counts
Base on which all of system is builtBase on which all of system is built Provides ground truth check of accounting systemProvides ground truth check of accounting system Key demographic data collected: location, relationship, sex, Key demographic data collected: location, relationship, sex,
age, race, Hispanic originage, race, Hispanic origin
Measure Death and Birth Measure Death and Birth ComponentsComponents
Birth RegistrationBirth Registration– Ties birth to place of residence of motherTies birth to place of residence of mother– Race data is for parents not child – and uses older classification Race data is for parents not child – and uses older classification
systemsystem– Completeness of registration is assumedCompleteness of registration is assumed
Death registrationDeath registration– Ties death to place of residence or last address?Ties death to place of residence or last address?– Race is not self reportedRace is not self reported– Completeness and speed of tabulation is an issueCompleteness and speed of tabulation is an issue
Estimating International Migration Estimating International Migration FlowsFlows
Legal immigrationLegal immigration– Difference between residence change and legal status changeDifference between residence change and legal status change– Problems with place of intended residenceProblems with place of intended residence– Completeness issuesCompleteness issues
Legal EmigrationLegal Emigration– Lack of data collection when leaving the countryLack of data collection when leaving the country– Problems of using other countries dataProblems of using other countries data
Illegal immigrationIllegal immigration– Methods are often indirectMethods are often indirect– Question of census coverage Question of census coverage
Alternative data from the American Community SurveyAlternative data from the American Community Survey
Measuring Domestic MigrationMeasuring Domestic Migration
Use of matched IRS returns to provide county in and out Use of matched IRS returns to provide county in and out migrationmigration
Coverage of IRS dataCoverage of IRS data Assigning age, race, hispanic origin, and sex dataAssigning age, race, hispanic origin, and sex data Timing of data collection and tabulationTiming of data collection and tabulation
Develop Yearly Population Develop Yearly Population Estimates and ControlsEstimates and Controls
Develop annual national, state, county, and place data for Develop annual national, state, county, and place data for funding and other administrative usesfunding and other administrative uses
Provide county age, race, sex, Hispanic origin controls for Provide county age, race, sex, Hispanic origin controls for the American Community Surveythe American Community Survey
Issues of timeliness and accuracy of input dataIssues of timeliness and accuracy of input data
Problems with an Accounting Problems with an Accounting SystemSystem
Errors in specifying the system can multiply over Errors in specifying the system can multiply over timetime
Errors in data input can cause faulty resultsErrors in data input can cause faulty results Structure of the system may change over timeStructure of the system may change over time
Reconcile with new decennial Reconcile with new decennial census datacensus data
Need to recalibrate estimates from demographic accounting with Need to recalibrate estimates from demographic accounting with decennial census resultsdecennial census results
Census coverage error vs. population estimation errorCensus coverage error vs. population estimation error
Incorporating “error of closure” corrections into new estimates.Incorporating “error of closure” corrections into new estimates.
Reconciling Inventory and Reconciling Inventory and Accounting SystemsAccounting Systems
Audit of the current demographic accountsAudit of the current demographic accounts
– Differences with a Population RegisterDifferences with a Population Register– Potential inconsistencies in the systemPotential inconsistencies in the system– Future Hazards and OpportunitiesFuture Hazards and Opportunities