Population projections

Question 1

Population projection

Answer 1

Attempt to answer questions about future population size. Based on current knowledge of population size and age structure, rates of birth, death, and migration, and assumptions about how quickly these rates will change.

Methods:

(1) Trend extrapolation/Mathematical Method
(2) Land-use techniques
(3) Economic-based techniques
(4) Cohort-component techniques

Question 2

Population projection: Trend extrapolation/Mathematical method

Answer 2

(1) Simple: linear, geometric, exponential (calculations same as in estimates section)
(2) Complex: linear trend, polynomial curve, logistic
(3) Ratio: constant-share, shift-share

Question 3

Population projection: Trend extrapolation/Mathematical method: Complex extrapolation or curve-fitting technique

Answer 3

Linear model: y = a + bx

Polynomial model: y = a + bx + cx^2 + … + zx^n (Gompertz curve, Logistic curve)

Question 4

Population projection: Trend extrapolation/Mathematical method: Regression methods

Answer 4

Simple regression
Multiple regression

Data requirement:
(1) Total population counts and/or symptom values for series of time period prior to estimate date.

Assumptions:

(1) Linear change in total population.
(2) Historical trends apply to current trends.

Question 5

Population projection: Trend extrapolation/Mathematical method: Ratio extrapolation techniques

Answer 5

Constant-share: Proportion of population of subareas remains same over time.
Share-shift method: Changes in proportion of total population of subareas remains same over time.

Question 6

Population projection: Land-use techniques

Answer 6

Example:
Given 2000 and 2010 Census population, project 2020 populations for census area(s).
Determine density cannot exceed 1,000 persons per square mile.
If particular area has too many people in it, redistribute population that cannot locate to another area.

Question 7

Population projection: Economic-based techniques

Answer 7

Projecting labor demands over time.
Projecting labor supplies over time.
Matching labor supplies and labor demands.
Determining levels of migration.
Projecting the total population changes accompanying the migration of labor.

Question 8

Population projection: Cohort-component techniques

Answer 8

Uses 3 components of population change.
Pt = P0 + Bt - Dt + NMt, where:

Pt = Population for estimate year
P0 = Population at base year
Bt = Births between P0 and Pt
Dt = Deaths between P0 and Pt
NMt = Net migration between P0 and Pt

4 steps:

(1) Selection of baseline set of cohorts for area of study.
(2) Determination of appropriate baseline migration, mortality, and fertility measures for each cohort for the projection period.
(3) Determination of the method for projecting trends in fertility, mortality, and migration rates over the projection period.
(4) Selection of a computational procedure for applying the rates (from step #3) to the cohorts over the projection period.

Question 9

Special populations

Answer 9

Populations where unlikely to show same patterns of change as general population. Usually treated by removing “special” populations from base populations, estimating or projecting “special” populations independently and then adding to projection of general population.

Group Quarters population: college dorms, prisons, nursing homes, long-term care homes, military barracks

Question 10

Computation of Net Migration

Answer 10

Vital Statistics Method

Forward Survival Method