Planning and Demography• Demography is the scientific study of human population.
Demographers are very interested in:1) Population size, 2) Population composition, 3) Population distribution,4) Causes of changes in these factors over time,5) Consequences of these changes over time.
• Demographers study in detail these changes over time, investigating issues such as changes in fertility rates, mortality rates, and migration.
• Planners are also very interested in these very same issues, but from a perspective of:
--how do population changes influence the demand for and provision of infrastructure and public services--how will population changes impact the environment--how do population changes influence changes in land use
Population Size• Population size: The number of people in a given geography at a
given time. U.S., Florida, and Leon County Population 1960-2000
USFLLC
• Natural Increase: The amount of population increase attributable to a greater number of births than deaths.
--In US in 1990, 17 births per 1000, 9 deaths per 1000a natural increase of 8 per 1000 (0.8%) (290 million)--World 1.8% per year for natural increase (6.26
billion)• Use the “Rule of 70” to determine doubling time: Divide 70 by
the growth rate. So World will double population in ~39 years (70/1.8 = ~39)
1960 1970 1980 1990 2000
179,323,175 203,211,926 226,545,805 248,709,873 281,421,906
4,951,560 6,789,443 9,746,324 12,937,926 15,982,378
74,225 103,047 148,665 192,493 239,452
Population Distribution• Population distribution: The location of population across
geography/space.
• Major shifts in population distribution occurred in the Twentieth Century in the United States:
--Concentration: Movement from Rural to Urban/Metro Areas
--Deconcentration: Movement from Central Cities to Suburbs
--Migration from the Rust Belt to the Sun Belt
• Planners are particularly interested in these changes and their impacts on the built and natural environments.
• These macro-level changes have tremendous impacts upon communities of all sizes and in all areas of the United States.
Concentration Illustrated
Roughly 4 of every 5 Americanslives in a metropolitan area now.
Deconcentration Illustrated
As of 2000, 1 of every 2 Americanslives in a suburban area.
Regional Shifts Illustrated
Regional Shifts Illustrated
Population Composition• Population composition: The characteristics of the
population.
• Among those characteristics of interest to demographers and planners are:
--Age--Sex--Race/Ethnicity
• Again, the United States experienced many changes in these attributes throughout the Twentieth Century:
--An aging population--The “rise of women”--An increasingly racially and ethnically diverse population
An Aging Population Illustrated
An Aging Population Illustrated
The “Rise of Women” Illustrated
A Diversifying Population Illustrated
A Diversifying Population Illustrated
Population Pyramids• One way of looking at changes in the composition of a population
is through Population Pyramids.
• Population pyramids show the composition of a population by age and sex (percent population in all age-sex cohorts)
• These pyramids typically show the following:
--Males on left side/Females on the right side
--Age groups as individual cohorts going from youngest on the bottom to oldest on the top
• These pyramids can be done for different geographies and/or different racial and ethnic groups.
U.S. Population Pyramids 1900, 1950, 2000
Florida’s Population Pyramid, 2000
5% 4% 3% 2% 1% 0% 1% 2% 3% 4% 5%
0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85+
Age
Coh
ort
s
Percent Population
Females
Males
Source: 2000 Census SF1, Table P12
5% 4% 3% 2% 1% 0% 1% 2% 3% 4% 5%
0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85+
Age
Coh
orts
Percent Population
Females
Males
Source: 2000 Census SF1, Table P12
Franklin County Population Pyramid, 2000
8% 6% 4% 2% 0% 2% 4% 6% 8%
0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85+
Age
Coh
ort
s
Percent Population
Females
Males
Source: 2000 Census SF1, Table P12
Leon County Population Pyramid, 2000
Measuring Population Change• Population change is simply the difference in population between
two points in time.
• Change can be expressed in Absolute or Percentage terms.
• Absolute Change: The simple difference between population figures. Negative values indicate a loss in population.
Florida’s Absolute Population Change 1990-2000Pop 2000 – Pop 1990 15,982,378 – 12,937,926 = 3,044,452
• Percent Change: The relative growth rate over a period of time calculated as a percentage using the formula: [(New-Old)/Old] *100
Florida’s Percent Population Change 1990-2000(Pop2000-Pop1990)/Pop1990*100
(15,982,378- 12,937,926)12,937,926
* 100 = 23.53%
U.S., Florida, and Leon County Population Change 1960-2000
U.S.
%Chg
Florida
%Chg
Leon Co
%Chg
1960 1970 1980 1990 2000
179,323,175 203,211,926 226,545,805 248,709,873 281,421,906
13.3% 11.5% 9.8% 13.2%
4,951,560 6,789,443 9,746,324 12,937,926 15,982,378
37.1% 43.6% 32.7% 23.5%
74,225 103,047 148,665 192,493 239,452
38.8% 44.3% 29.5% 24.4%
Example Percent Population Change Analysis
• Florida and Leon County grew at much faster rates than the United States as a whole during the period 1960-2000. • Leon County’s growth mirrored that of Florida’s during this period.
Components of Population Change• Demographers rely upon the “Demographic Balancing Equation”
to very simply and elegantly summarize population change:
Pop2 = Pop1 + B – D + IM – OM, where
Pop2 = Population at a later time period
Pop1 = Population at an earlier time period
B = Births
D = Deaths
IM = In-Migration
OM = Out-Migration
• The nature of population change is simple… changes can only occur through: 1) Births, 2) Deaths, or 3) Migration
Migration
Mortality
Fertility
Fertility Component• Fertility: The number of births that occur to an individual or in a
population.
• Fecundity: The physiological ability of individuals or couples to have children. Maximum fecundity for a population is believed to be 15 children.
• Another key concept is the “at-risk population”. Only a certain subset of the population is “at-risk” for fertility Women aged 12-50
• Factors that affect fertility include:1) Gender (Duh!) 4) Socioeconomic status2) Age 5) Others Religion, Culture,
Education3) Race/Ethnicity
• Common calculations related to fertility include:1) Total Fertility Rate: Average # of children in a “synthetic” family2) General Fertility Rate: #Births per 1000 women of childbearing age3) Crude Birth Rate: # Births/Midyear Population
Mortality Component• Mortality: Analyzes the number and causes of deaths in a population.• Life Span: The upper limit to human lives is theorized to be
somewhere around 120, although there are reports of some people living as long as 135 years.
• Factors affecting mortality include:1) Age (J-curve) 4) Race/Ethnicity 2) Gender 5) Modernity3) Socioeconomic status
• Common calculations related to mortality include:1) Overall Death Rate: Deaths per 1000 population 2) Crude Death Rate: # Deaths/Midyear Population 3) Age-Sex-Race specific survival rates: The likelihood that an individual with certain characteristics will survive the year 4) Life Expectancy: The expected number of years an individual will live if they were to live their entire life right now.
In 1900~30 (worldwide) By 2000~70 (worldwide)
Theory of the Demographic Transition• When taken together, mortality and fertility can combine to form four
scenarios:
• It is theorized that as countries move from less developed to more developed, they transition from a High Birth/High Death society to one of Low Birth/Low Death. It is during this transition that (it is theorized) developing countries experience a population boom. Why?
Mortality
Low High
Fertility
Low USA, Japan, W. Europe, Aus.
None
High Southern Africa, Latin Amer.Asia (parts)
Northern Africa,Asia (parts)
Migration Component• Migration: The movement of people into and out of a certain area.
• Migration can occur at all geographic levels.1) Neighborhood 2) Within a county3) Across states: Out-migration versus In-migration4) To a different country: Emigration (out of a country) versus Immigration (into a country)
• Migration in the United States:Approximately 20% of Americans move per yearAmericans move about 11 times over their lifetimes (on
average)
• Factors affecting migration include 1) Age2) Gender 3) Socioeconomic Status4) Race and Ethnicity
Major State to State Migration Flows
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