Transcript Recent European Emigration to the United States

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
– Are used for planning and policy decisions
 Population Projections
– Project trends beyond the time interval of the input data
– Use mathematical models of varying sophistication
– Often use models of components of demographic change: births,
deaths, migration, and immigration
 Population Estimates
– Estimate population using data from the same time period
– May use demographic data: births and deaths
– May use indicator variables – housing, administrative records
Projection: Simple Extrapolation
P
x+1
t+1
=
x
(P t
)
x
((P t
)/(P
x-1
t-1))
where,
x
P t is the population age x in a given place at
time t
U.S. Population: Census Counts from
1790 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 Using
Components of Change
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Begins with a measured base population (census, etc)
Calculates trends in births, death, migration
Usually based on cohort-component method
May used multi-regional projection matrix methods
Accepted method for official U.S. population projections
Migration
• Population A
by age, race,
and sex
Place B
• Population B
by age, race,
and sex
Place A
Migration
• Population C
by age, race,
and sex
Place C
Component-based Projections
P
x+1
t+1
=
x
Pt
x
x
x
+ B (if x<0) - D + I - O
where,
x
P 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+1
x
D is then number of deaths age x in a given place between t and t+1
x
I is the number of in-migrants age x to a given place between t and t+1
x
O is the number of out-migrants age x from a given place between t
and t+1.
Development of Demographic
Accounting Approach
– Nationwide birth and death registration began in the early 1900’s
– Estimates and projections for states, counties, and places
developed in the last half of the 20th century
– Demographic Analysis became a key tool to evaluate decennial
census quality
– “Integrated” accounting system implicit in the American Community
Survey for the 21st century
Elements of US Demographic
Accounting System
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Master Address Files
Decennial Censuses
Birth and Death Registers (NCHS)
Immigration Data (INS & ACS)
Domestic Migration Data (IRS)
Adjustments and Corrections
American Community Survey
Master Address Files
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Importance of tying population to geography
Address canvassing prior to census year
Corrections during census operation
Updates between censuses
Provides “frame” for census and survey operations
Issues with permits, construction, demolitions, and
conversions
 Addresses vs. physical location.
Decennial Census Counts
 Base on which all of system is built
 Provides ground truth check of accounting system
 Key demographic data collected: location, relationship,
sex, age, race, Hispanic origin
Measure Death and Birth
Components
 Birth Registration
– Ties birth to place of residence of mother
– Race data is for parents not child – and uses older classification
system
– Completeness of registration is assumed
 Death registration
– Ties death to place of residence or last address?
– Race is not self reported
– Completeness and speed of tabulation is an issue
Estimating International Migration
Flows
 Legal immigration
– Difference between residence change and legal status change
– Problems with place of intended residence
– Completeness issues
 Legal Emigration
– Lack of data collection when leaving the country
– Problems of using other countries data
 Illegal immigration
– Methods are often indirect
– Question of census coverage
 Alternative data from the American Community Survey
Measuring Domestic Migration
 Use of matched IRS returns to provide county in and out
migration
 Coverage of IRS data
 Assigning age, race, hispanic origin, and sex data
 Timing of data collection and tabulation
Develop Yearly Population
Estimates and Controls
 Develop annual national, state, county, and place data for
funding and other administrative uses
 Provide county age, race, sex, Hispanic origin controls for
the American Community Survey
 Issues of timeliness and accuracy of input data
Problems with an Accounting
System
 Errors in specifying the system can multiply over
time
 Errors in data input can cause faulty results
 Structure of the system may change over time
Reconcile with new decennial
census data
 Need to recalibrate estimates from demographic
accounting with decennial census results
 Census coverage error vs. population estimation error
 Incorporating “error of closure” corrections into new
estimates.
Reconciling Inventory and
Accounting Systems
 Audit of the current demographic accounts
– Differences with a Population Register
– Potential inconsistencies in the system
– Future Hazards and Opportunities