Lane County 20-Year Coordinated Population Forecast Project

Kick-off Public MeetingDecember 2, 2008

Population Forecasting Techniques

Presentation by Population Research Center

Project Team

Population Research Center Project Team

Risa Proehl, Project LeadDanan Gu, Demographic Analyst

Ken Radin, GIS AnalystGeorge C. Hough Jr., Director

Population ForecastsProcess

Develop Demographic Models Using Historic and Recent Data

Analyze Past and Recent Population Trends - Reasons for Change, Continuous or Short-term?

Gather Information About Recent and Planned Future Housing and Population change (housing developments, construction of new GQ facilities, new employers)

Make Assumptions About Future Housing and Population Change

Revise Forecasts on a Regular Basis

Outline

Population Trends – Lane CountyPopulation Projection MethodsAssumptions About the Future

Population Change in Lane County

Lane County Grew Consistently 1900 to 2008 Lane County Grew in Absolute and Relative

Reflecting Societal/Economic Conditions Lane County Population Change Has Shifted from

High Growth Scenario of 3% per year to about 1% per annum

The Eugene and Springfield Shares of County Population Increased but Have Become More Stable in Recent Years

Lane County Grew Consistently Over the Past Century

Population Change 1900 to 2008 Reflects Decade Economic Changes

Higher Growth and Lower Growth Periods

City Population Shares Have Stabilized Over Recent Times

Population Projection TechniquesPrimary Models for this Study

COHORT-COMPONENT METHODfor Lane County, Eugene, SpringfieldRelies on Age-Sex Schedules of Demographic BehaviorPopulation Pyramid Displays Age StructureMortality – Fairly Constant over TimeFertility – Decreased Teen Fertility, Older Mothers and

Latino BirthsMigration – In Lane Co., Mostly Influenced by Common

College Pattern and Employment AvailabilityMigration Rates Subject to Greater Fluctuation than

Mortality and Fertility and more unpredictableThree Scenarios of Growth: High, Medium, Low

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+

-20000 -15000 -10000 -5000 0 5000 10000 15000 20000

Population Distribution, Lane County, 1990 and 2000

Males Females

-20000 -15000 -10000 -5000 0 5000 10000 15000 20000

0-45-9

10-1415-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980-84

85+

1990

2000

Population

Age Schedules of Fertility, Mortality and Migration Determine the Age Structure of a Population

Age Schedules of Fertility, Mortality and Migration Determine the Age Structure of a Population

Mortality Age Schedules Are Similar for 1990 and 2000

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 1--4 5--14 15-24 25-34 35-44 45-54 55-64 65-74 75-84 85+

1990 2000

Deat

h ra

te

Age

Fertility Schedules Are Similar for 1990 and 2000

Migration Schedules Show Dominance of College Migration

Population Projection TechniquesPrimary Models for this Study, con’t.HOUSING UNIT METHODfor Ten Smaller Cities, Unincorporated Area, Area Outside UGBs

Housing Unit Growth – Trend Actual, Trend County SharesHousing Unit Type (single-/multi-family)Household Composition – PersonsPersons Per HouseholdOccupancy RatesAdd Group Quarters PopulationBased on Medium Growth Scenario – one scenario as smaller areas have more variability than larger areasControlled to Cohort-Component Model Results for County

Housing Unit Method, con’t.

Fluctuations in housing unit growth follows economic trends with Exceptions

PPH Factors that influence PPH:

Race/Ethnicity, Age (fertility), Economy

Generally Decreasing in U.S. Occupancy Rates - Seasonal Housing

Ranges from 79% to 95% Group Quarters Population Ranges from

0% to 5% of Total Population Doesn’t Fluctuate Greatly (unless

new facility built or closed)

Average Annual Number of Housing Units Added

0

20

40

60

80

100

120

140

160

COTTAGE GROVE FLORENCE

1970s 1980s 1990s 2000-08

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

EUGENE SPRINGFIELD UNINCORP

1970s 1980s 1990s 2000-08

0

10

20

30

40

50

60

70

80

90

CRESWELL DUNES CITY JUNCTION CITY OAKRIDGE VENETA

1970s 1980s 1990s 2000-08

0

1

2

3

4

5

6

7

8

9

10

COBURG LOWELL WESTFIR

1970s 1980s 1990s 2000-08

Housing Unit Method, con’t.

PPH 1990 2000 2007

COBURG 2.41 2.64  

COTTAGEGROVE 2.60 2.54  

CRESWELL 2.68 2.76  

DUNES CITY 2.30 2.23  

EUGENE 2.30 2.27 2.25

FLORENCE 2.21 2.02  

JUNCTIONCITY 2.42 2.55  

LOWELL 2.90 2.72  

OAKRIDGE 2.45 2.35  

SPRINGFIELD 2.54 2.54  

VENETA 2.79 2.85  

WESTFIR 2.84 2.76  

UNINCORP 2.69 2.58  

LANE CO 2.49 2.42 2.41

2000Occ. Rate GQ

COBURG 95% 0

COTTAGE GROVE 95% 152

CRESWELL 95% 58

DUNES CITY 79% 0

EUGENE 95% 6,078

FLORENCE 85% 56

JUNCTION CITY 95% 138

LOWELL 92% 0

OAKRIDGE 88% 0

SPRINGFIELD 95% 635

VENETA 95% 0

WESTFIR 94% 0

UNINCORP 93% 302

LANE CO 94% 7,418

Population Projection Techniques

For Comparison and to Serve as a CheckShift-Share and Other Ratio MethodsTrend ExtrapolationSimple Economic/Employment ModelLand Use and CapacityAdditional Housing Unit Models (in addition to CC

models)

Other Models/Techniques to Considerfor All Areas in this Study

Data

Background Information Some Entered Directly into Projection Models Some Provide Support for Assumptions Made for

Future Change All Data Available for Lane County, Many Available

for Individual Cities (Census, Land Use, Housing, Births, Group Quarters Population)

Data Data Sources

1990 and 2000 Census Data ACS Data – post-2000 Vital Statistics Building Permit Data Annual Housing and Population Data from Local Jurisdictions PRC Annual Population Estimates, post-2000; Revised to

Current Boundaries and UGBs School Enrollment Data Land Use Data and Plans for Future Development Local Studies – e.g., School Enrollment Projections, Previous

Coordinated Plans, TSP Employment and Labor Force Data and Projections Previous OEA/DAS–County Projections to 2040 Confer with OEA about Current and Revised Forecast Information from local Government Staff, Public Meetings

Future Conditions and Considerations

Assumptions are Based on Past and Recent Trends, Occurrence of Events, and Plans for Future Housing

Future Assumptions for Lane County? Mortality – Slight Increase in Longevity Fertility – Slightly Older Mothers and Latino Births Migration – Employment and Group Quarters

Populations Assumptions about PPH, Vacancy Rates, Housing

Construction Some Current Conditions are Assumed to be the Same

in Future (e.g. land use zoning, residential densities, UGBs expand as needed)

Citizen and Governmental Input Combined with Demographic Expertise Will Produce the Most Reasonable or Likely Forecasts

High: Assuming average annual increase rate from 1970-2005.Medium: Assuming average annual increase rate from 1990-2005.Low: Assuming average annual increase rate from 2000-2005. (Ann. Time Series)

Life Expectancy, Lane County, 1970-2035

Estimates after 2005

Total Fertility Rate, Lane County, 1990-2035

Mean age at births, Lane County,1970-2035

Population Growth, Net Migration, Lane County, 1980-2005Population Growth, Net Migration, Lane County, 1980-2005

Pop

ula

tion

Pop

ula

tion

Net

mig

rate

rate

( p

er

1,0

00)

Net

mig

rate

rate

( p

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1,0

00)

YearYear

Projections and ForecastsGeneral Comments

Projections Are More Accurate in Short-Term The Larger the Geographic Area, The More Accurate

the Projection Population Forecast is a Tool to Help with Planning and

Serves as a Guide – not a Guarantee of What Will Occur

Revisions to Forecasts Should be Made Regularly! PRC Utilizes Best Practices – Professional Associations