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