Table Of ContentThe Springer Series on Demographic Methods
and Population Analysis 37
Stanley K. Smith
Jeff Tayman
David A. Swanson
A Practitioner's
Guide to State and
Local Population
Projections
A Practitioner’s Guide to State and Local
Population Projections
THE SPRINGER SERIES ON
DEMOGRAPHIC METHODS AND
POPULATION ANALYSIS
Series Editor
KENNETH C. LAND
Duke University
Inrecentdecades,therehasbeenarapiddevelopmentofdemographicmodelsandmethods
and an explosive growth in the range of applications of population analysis. This series
seekstoprovideapublicationoutletbothforhigh-qualitytextualandexpositorybookson
modern techniques of demographic analysis and for works that present exemplary
applications of suchtechniques tovarious aspectsof populationanalysis.
Topicsappropriate fortheseries include:
(cid:129) General demographic methods
(cid:129) Techniques of standardization
(cid:129) Life table modelsand methods
(cid:129) Multistate and multiregional lifetables, analyses andprojections
(cid:129) Demographic aspects ofbiostatistics and epidemiology
(cid:129) Stable populationtheory and its extensions
(cid:129) Methods ofindirect estimation
(cid:129) Stochastic population models
(cid:129) Event historyanalysis, duration analysis,and hazard regressionmodels
(cid:129) Demographic projection methods andpopulation forecasts
(cid:129) Techniquesofapplieddemographicanalysis,regionalandlocalpopulationestimatesand
projections
(cid:129) Methods ofestimation and projectionfor business andhealth care applications
(cid:129) Methods andestimates forunique populationssuch asschoolsand students
Volumes in the series are of interest to researchers, professionals, and students in
demography,sociology,economics,statistics,geographyandregionalscience,publichealth
and health care management, epidemiology, biostatistics, actuarial science, business, and
related fields.
For furthervolumes:
http://www.springer.com/series/6449
Stanley K. Smith (cid:129) Jeff Tayman
David A. Swanson
A Practitioner’s Guide
to State and Local
Population Projections
StanleyK.Smith JeffTayman
BureauofEconomicand EconomicsDepartment
BusinessResearch UniversityofCalifornia-SanDiego
UniversityofFlorida SanDiego,CA,USA
Gainesville,FL,USA
DavidA.Swanson
DepartmentofSociology
UniversityofCaliforniaRiverside
Riverside,CA,USA
ISSN1389-6784
ISBN978-94-007-7550-3 ISBN978-94-007-7551-0(eBook)
DOI10.1007/978-94-007-7551-0
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Foreword
Alargepartofourdailylivesisgovernedbynumbers.Howmanyhoursofsleepdid
Igetlastnight?Howmanyunreadmessagesarequeuedupinmyinbox?Howmany
“friends”doIhaveonFacebook?What’stheupcomingPowerballpayoff?How’s
mycholesterolcountdoing?CanIrecallmydaughter’sphonenumber,mygrand-
daughter’s birthday? Numbers such as these encompass portions of our personal
and shared social reality. They roll around in our head, and they are part of what
determineourmood,ourbehavior,well-being,worries,andactivityconstraints.
Populationprojectionsalsopresentuswithnumbers.Butthesearenumbersofa
very different nature. Rather than simply reflecting a social reality (and associated
beliefsandbehaviors),theyservetocreatearealitybasedonanticipation—areality
unwitnessed,unobserved,andlargelyunknown.Yet,onthebasisofsuchnumbers,
schoolsarebuilt(orclosed),roadsarewidened,airportterminalsexpanded,munic-
ipal services extended, and marketing strategies altered. So this book is about the
secondkindofnumber,thesortleadingtoanticipatorybehaviorsand,occasionally,
preemptiveactions.Itistheapplieddemographer’sdifficultroletocreativelydeploy
thedata,tools,andperspectivesofthepopulationsciencestocarryoutthesetasksnot
onlyethicallyandtransparentlybutwithanexperiencedanddisciplinedhand.This
bookprovidesamarvelouslyclear,well-organized,andcomprehensiveblueprintfor
understandingandcompetentlyperformingthisrole.
Theauthorsareseasonedapplieddemographicpractitioners.Theyhaveindivid-
ually and collaboratively contributed mightily to the demographic literature. The
book is intellectually solid, methodologically encompassing, and—while retaining
thehistoricallyinterestingmaterial—firmlycontemporaryanduptodate.
Early in my own career, one of my mentors rhetorically asked, “Why do we
make population projections? They always turn out to be wrong, so why do we
persist?” Aftera brief excursionthroughthe standardreasonsfor why projections
are useful, he added, “Probably the most important reason for engaging in this
enterpriseissothatwelaterknowwhattobesurprisedabout.”Wonderfullysaid!
The point is that we live in a world of frenetic change. We are so habituated to
mindlesslyaccommodatingtothischangethatwerarelypauselongenoughtosay
“Wow!”andtoreflectonwhatwethought,justafewyearsback,ourpresentreality
v
vi Foreword
might look like. Projections and forecasts prepared yesterday permit us to do that
today.Today’sprojectionswillservethatpotentiallychasteningpurposetomorrow.
The overall narrative and thoroughly developed methodologies in A Practi-
tioner’s Guide to State and Local Population Projections will, of course, not
eliminate all of tomorrow’s surprises. One can indeed hope, however, that practi-
tionerswhowiselyselecttousethisbooktoguidetheirowndemographicpursuits
will benefit from the authors’ skillful verve, their richly detailed methodological
coverage, and the numerous concrete examples presented throughout the material
tominimizethenumberandmagnitudeoffuturesurprises.
Thisvaluablecompendiumpresentsmethodsthataretriedandtestedalongside
those that are recent and innovative. The book revisits and updates most of the
topicstreatedintheauthors’earlierbook,StateandLocalPopulationProjections:
MethodologyandAnalysis.However,thecurrentbookshouldnotbeunderstoodas
arevisededition.Freshattentionisgiventoemergingmethodologicalapproaches
in small-area population forecasting (projecting) and, in particular, to new data
resources that have fundamentally altered the information content of forecasting
models. The material is treated with originality and conviction and benefits
immensely from real-life illustrations drawn from the authors’ own work. With A
Practitioner’s Guide to State and Local Population Projections, Smith, Tayman,
and Swanson have again secured their leading place as careful, practical, and
solidlycompetentapplieddemographicscholars.
UniversityofNorthCarolinaatChapelHill PaulR.Voss
June2013
Preface
A lot has happened since we published State and Local Population Projections:
MethodologyandAnalysisin2001.Smartphones,electronictablets,andtheCloud
have given us access to virtually endless sources of information, no matter where
we are. Improvements in technology, software, and computing hardware have
expanded the way we access, store, and analyze information. Facebook, Twitter,
andothersocialmediasiteshavechangedthewaywecommunicate.Globalization
hasalteredtheworld’seconomicsystemand9/11changedalmosteverything,from
internationalrelationstothewayweboardairplanes.
Alothashappenedinthefieldofapplieddemographyaswell.Datasourceshave
proliferated, methods have advanced, computing capabilities have mushroomed,
andnewresearchhasbeenpublished.Onemajorchangeisthatthedecennialcensus
no longer includes a long form collecting detailed socioeconomic, demographic,
andhousinginformationfromasampleofcensusrespondents.Thisinformationis
nowcollectedintheAmericanCommunitySurvey(ACS),whichdiffersinseveral
ways from the census long form. Particularly important for the production of
populationprojectionsisthattheACScollectsdatacontinuouslyratherthanonce
per decade, is based on a smaller sample size, uses different residence rules, and
measuresmigrationovera1-yearratherthana5-yearperiod.
Theseandotherchangeshave convinced usthatanew bookonstate andlocal
population projections is needed. This new book retains and updates much of the
materialincludedinourpreviousbook,butcoversanumberofnewtopicsaswell.
We present a detailed discussion of the differences between ACS migration data
andthemigrationdatacollectedinthedecennialcensus,payingparticularattention
to how these differences affect the construction of cohort-component projections.
We provide an illustration of how to use ACS migration data to project a county
population. We add a new chapter on projections of population-related variables
suchashouseholds,schoolenrollment,laborforceparticipation,andpersonswith
disabilities. We expand our discussion of microsimulation models, scenario anal-
ysis, special populations, international migration, and the benefits of combining
vii
viii Preface
projections from several different models. Throughout the book, we incorporate
research findings that have appeared in the literature since the publication of our
previousbook.
As before, we pay particular attention to problems encountered when making
projections for small areas (e.g., counties and subcounty areas). We describe a
number of data sources and projection methods, focusing on those that are most
accessibleandcanbeusedinavarietyofcircumstances.Wediscussthestrengthsand
weaknessesofeachandprovideourthoughtsonwhicharemostusefulforparticular
purposes. We include many examples and illustrations, as well as equations and
verbaldescriptions,inanattempttopresentthematerialasclearlyaspossible.
A number of methods, data sources, and application techniques can be used for
constructingstateandlocalpopulationprojections.Decidingwhichonestoinclude—
and how to present them—was not an easy task. We wanted the book to be
comprehensivebutnotlong-winded,technicallyprecisebutnotoverlymathematical,
clearlywrittenbutnotsimplistic.Wewantedittobeusefultoanalystswithastrong
background in demography yet accessible to those with little or no demographic
training. Most important, we wanted it to provide practical guidance to demogra-
phers,planners,marketanalysts,andotherscalledupontoconstructorevaluatestate
andlocalpopulationprojectionsinreal-worldsettings.Thereaderwillhavetodecide
whetherwehavesucceededinaccomplishingtheseoften-conflictinggoals.
We thank Paul Voss for writing the foreword to this book. It would be impos-
sible tofindapersonmorequalified than Paul, givenhis numerous andimportant
contributionstothefieldofapplieddemography.WealsothankEvelienBakkerand
Bernadette Deelen-Mans for shepherding the book through Springer’s production
process;theirassistancewasinvaluable.
Aboveall,weexpressourgratitudetoourwives—Rita,Melinda,andRita—for
theirlove,encouragement,andpatienceasweworkedonthisbook.
Contents
1 Rationale,Terminology,Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 WhatIsaPopulationProjection?. . .. . . . . . .. . . . . . .. . . . . . .. 2
1.1.1 Projections,Forecasts,Estimates. . . . . . . . . . . . . . . . . . . 2
1.1.2 AlternativeApproaches. . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 WhyMakePopulationProjections?. . . . . . . . . . . . . . . . . . . . . . . 6
1.2.1 RolesofProjections.. . . . .. . . . . .. . . . .. . . . .. . . . . .. 6
1.2.2 ProjectionsandDecisionMaking. . . . . . . . . . . . . . . . . . . 8
1.2.3 ForecastingandPlanning. . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3 HowCanThisBookHelp?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3.1 Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3.2 GeographicFocus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.3.3 Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.3.4 TargetAudience. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 FundamentalsofPopulationAnalysis. . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 DemographicConcepts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.1 Size. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1.2 Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1.3 Composition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.1.4 Change. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.2 ComponentsofChange. . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . 27
2.2.1 Mortality. . . .. . . .. . . . .. . . .. . . . .. . . . .. . . .. . . . .. 28
2.2.2 Fertility. . .. . . . .. . . . .. . . . .. . . . .. . . .. . . . .. . . . .. 28
2.2.3 Migration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.2.4 DemographicBalancingEquation. . . . . . . . . . . . . . . . . . 29
2.3 StatisticalMeasures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
ix
