An Introduction to the U.S. Demographic System John F. Long

Introduction  U.S. demographic system evolved over time: –Rough guesswork in colonial times –Decennial censuses since 1790 –Birth and death registration in the early 1900’s –Estimates and projections in the last half of the 20 th century –“Integrated” Accounting system implicit in the American Community Survey

Inventory vs. Accounting  Inventory Approach –Population Stocks –Decennial Census Enumeration –Independent Counts –Mechanism of Population Change Ignored  Accounting Approach –Population Flows –Tracking of Components of Population Change –Estimates and Projections –Demographic Analysis  Combined Approach

Inventory Approach Pre-school Lunchboxes Bin A School Lunchboxes Bin B Workman’s Lunch kits Bin C

Population A by age, race, and sex Place A Population B by age, race, and sex Place B Population C by age, race, and sex Place C Decennial Census Counts

U.S. Population: Census Counts from 1790 and Projections for Source: U.S Census Bureau, Decennial Censuses ; Abraham Lincoln, “Annual Message to Congress: December 1, 1862”.

Need for an Accounting System  To estimate population change between censuses  To explain population change  To aid government and business policy and planning  To project future population  To plan and evaluate censuses

Pre-School Lunchboxes Bin A School Lunchboxes Bin B Workman Lunchkits Bin C

Population A by age, race, and sex Place A Population B by age, race, and sex Place B Population C by age, race, and sex Place C Migration

Basic Demographic Accounting P x+1 t+1 = P x t + B (if x<0) - D x + I x - O x where, P x 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 D x is then number of deaths age x in a given place between t and t+1 I x is the number of in-migrants age x to a given place between t and t+1 O x 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 20 th century –Demographic Analysis became a key tool to evaluate decennial census quality –“Integrated” accounting system implicit in the American Community Survey for the 21 st century

Elements of US Demographic Accounting System  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  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

Pre-School Lunchboxes Workman Lunchkits Bin A Workman Lunchkits School Lunchboxes Bin B Workman Lunchkits Misc Junk Bin C Extra Inventories Fired Boss More Overtime Pay !

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