tennessee population projections matthew c. harris, ph.d. assistant professor, economics center for...
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Tennessee Population Projections
Matthew C. Harris, Ph.D. Assistant Professor, Economics
Center for Business and Economic Research
Demographic Data - Sources
• Decennial Census
• American Community Survey
• Census Bureau Population Estimates
• Population Projections
Decennial Census
• Mandated by Article 1, Section 2 of U.S. Constitution
• Based on actual counts of persons• Used to determine number of members in
House of Representatives from each state• Provides the base population for the
annual population estimates series
Population Estimates
• Calculated number of people living in an area at a specific point in time.
• Derived using models that account for changes in:• Births• Deaths• Net Migration
• Used to control/inform ACS, CPS, etc.• Used for denominators by state/local government
agencies and non-profits as denominators in rate calculations and program fund allocations.
Population Projections
• Estimates of the population for future dates
• Relies on assumptions about future births, deaths, and net migration.
• Used by government, business, and non-profits for planning purposes and demand forecasts.
What We Do
• A ‘cohort-component’ model• Single Age – Sex – Race/Ethnicity - County
• Birth: county-age-race specific birth rates• Death: Statewide death rates, augmented
by SSA tables for changing life-expectancy.
• Net Migration – Use decennial census data.
Invisible Forces
• Net Migration is Unobservable• Birth and death are documented in vital statistics
‘Tennessee Department of Health’• Net migration is the ‘residual’
• Population is known• Births are known• Deaths are known• Net Migration makes up the difference
• Most volatile component of population change• Most critical component of short-term population
change.
TN Doing What TN Does
• From a population standpoint: • Grow at about 1.0% per year on average• Noisily
• 1930’s – 11.4% Growth• 1940’s – 12.9% Growth• 1950’s – 8.4% Growth• 1960’s – 10.0% Growth• 1970’s – 17.0% Growth • 1980’s – 6.2% Growth• 1990’s – 16.7% Growth• 2000’s – 11.5% Growth• 2010’s – 8.0% Growth (at current pace)
What We Project - Statewide
2020: 7.1M
2030: 7.8M
2040: 8.5M2050: 9.3M
Approx. 1% Growth
All of this has happened before
All of this will happen again
Cohort Component Model
• We model population growth as a pure population process. • Births• Deaths• Historical Net Migration
• We do NOT include structural economic factors:• Structural Economic Changes• Planned Development• Infrastructure Changes
Why we exclude economic data
• To include economic data in a model, you need:• Consistent variables and consistent impact.
• An issued commercial development permit has to mean the same thing in County X as it does in County Y.
• Accurate forecasts of all economic variables included.• When accurate, including economic variables may be helpful.• Forecast error in economic variables may (and often does) make
overall population forecasts less accurate.
• Most economic variables are even noisier than net migration.
• Incorporating them ALSO requires an understanding of who those variables bring in to a given county.
• Population growth is actually a pretty stable process.
A compounding effect
𝑌=𝑋 𝛽+𝜖
Outcome(e.g., Population)
Things we can observe
Effect of Things we can
observe on the Outcome
Things we cannot observe
Short term gain, long term pain
Pop
Economic Activity
IndicatorsWRONG
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Key Trends from the Projection
2010201320162019202220252028203120342037204020432046204920522055205820612064
0 2,000,000 4,000,000 6,000,000 8,000,000 10,000,000 12,000,000
County Population by Race
Black Non-HispanicHispanicOther Non-HispanicWhite Non-Hispanic
Population
Year
A few key numbers on race
• 2010: • 75.6% White Non-Hispanic• 16.5% Black Non-Hispanic• 4.6% Hispanic• 3.2% Non-Hispanic, NWoBA.
• 2040:• 63.6% White Non-Hispanic• 17.2% Black Non-Hispanic• 11.1% Hispanic• 7.9% Non-Hispanic, NWoBA
Hispanic Population Growth
• 1990: 32,741• 2000: 123,838
• 278% Growth
• 2010: 290,059• 134% Growth
• 2020: 461,704 (projected)• 59% Growth
• 2030: 678,738 (projected)• 47% Growth
• 2040: 954,115 (projected)• 40.5% Growth
Age Histogram, 2010
Age under 5
5 to 9 10 to 14
15 to 19
20 to 24
25 to 29
30 to 34
35 to 39
40 to 44
45 to 49
50 to 54
55 to 59
60 to 64
65 to 69
70 to 74
75 to 79
80 to 84
85 and up
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
500000
Age Histogram, 2040
Age under 5
5 to 9 10 to 14
15 to 19
20 to 24
25 to 29
30 to 34
35 to 39
40 to 44
45 to 49
50 to 54
55 to 59
60 to 64
65 to 69
70 to 74
75 to 79
80 to 84
85 and up
0
100000
200000
300000
400000
500000
600000
Births Per Year – United StatesYear Births
1915-1925 Approx 2.9M PA1930 2.6M1935 2.3M1940 2.5M1945 2.8M1950 3.6M1955 4.1M1957 4.3M1960 4.2M1964 4.0M
1965-1989 3.1M-3.9M, trough in OPEC Years1990 4.2M
2000’s 4.0-4.1M2010’s 3.7-3.8M
Urbanization
• 10 Largest Counties 2010: 53% of TN Pop
• 10 Largest Counties 2040: 56% of TN Pop
• 10 Largest Counties 2060: 60% of TN Pop
Shelby Davidson Knox Rutherford Hamilton
Williamson Montgomery Sumner Sullivan Blount
Top 10 – Absolute ChangeCounty Absolute Population Change 2010-2040
Rutherford 275,106
Davidson 250,427
Williamson 222,432
Knox 152,180
Shelby 148,936
Montgomery 138,908
Wilson 93,888
Hamilton 90,081
Sumner 84,704
Sevier 58,441
Mid-cap GrowthCounty Absolute Population Change 2010-2040
Sevier 58,441
Washington 43,677
Robertson 35,564
Maury 32,178
Bradley 29,380
Tipton 28,182
Putnam 27,134
Cumberland 25,979
Madison 23,589
Fayette 23,511
Top 10 – Growth RateCounty CAGR 2010-2040
Williamson 2.68%
Rutherford 2.41%
Wilson 2.02%
Montgomery 1.99%
Sevier 1.68%
Fayette 1.60%
Robertson 1.44%
Sumner 1.42%
Sequatchie 1.37%
Loudon 1.29%
Growth Rate 11-20County CAGR 2010-2040
Cumberland 1.27%
Tipton 1.27%
Blount 1.14%
Davidson 1.12%
Maury 1.12%
Bedford 1.10%
Putnam 1.06%
Washington 1.01%
Knox 1.01%
Dickson 0.99%
(865) [email protected]