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.I '/" II/,//!Projecting future population growth involves a mechanically simple pro-fr.'The following discussions concern the methOds nduthe date of thi·s population and the first projection and the time inter al sepa-assumptions used toassemble the statistical information presented in this report.discussion focuses upon the pop lation proJ·cctions.rating all subsequent projections, is called the projection period.The firs tTh.esc projections \olereprepared using conventionar techniques of population analysis.The lengthof this period will be generally either one year or five years, depending upon di cussion concerns commitment and d3This procedure can be summarized in the follO\"ring manner. Consider"nn initial population distributed by age and sex. The time interval betweenccdurc.METHODS AND ASSUMPTIONSThe secondthe age convention.etentlon projections; they were derivedPopulations distributed by single years of age will pro-duce annual projections, \.,rhile populations arrayed in five-year age groups \"r111from the population projections to .lnsure consistent results and continuityproduce quinquennial projections.The logic of this statement should be appar-of methods and assumptions.IPopulation Projections.An initial age distributionpopulation projestions.represents the point of departure for allsus figures were not used, howevera midyearbasi I',bJuly 1.2groups and sex is to be projected for one projection period.tained from appropriate Itfe tables are applied toThe actual cen-, 'scause the projections were prepared on"A minor adjustment was necessary to convert the reportedage distributions from the original dateSuppose now, that an initial population distributed by quinquennial agein the projection procedure involves cohort survivorship.The initial age distribution for the Delaware pro-jections were derived from the 1970 Cer-sus of Population.1ent to readers at all levels of sophistication.the initial population.t eThe first stepSurvival ratios ob-age and sex cohorts inThis determines the expected age and sex compositionfor the projected population above age five.The second step in the procedureis to estimate the number of births during the prOjection period.There areof April 1 to the midyear date ofThe estimated i itial populations by age and sexseveral ways in which this can be done, but the most defensible technique inare shown in thefirst column of table 1.M Ivalves using a schedule of birth rates hy age of mother."These rates are ap-'plied to the female cohorts of childbearing age in the average of the initial# ititand projected populations to yield the quinquennial birth cohort.The sex di'S-·,1,111U. S. ilureau of the Census, Census of POjlulation:C It a r a.;.;c.;.;t.;.;c.;;.r.:;:i.:.:.:s:.::t:.:::i:.::c s, FinaIR,epor't PC ( I ) -D9 Dc la .,rarc, Table 138,, 1970 Dctllilcdpp. 9-183.IIIi2U .nlted Nations, Department of Economicand Social Affairs, Methodsof Estlmnting Basic Demographic NC.:lsurcs fromIncompleteData (Sl'/SOA/SeriesA/42), 1967, p. 58.- 2 -tribtltionof this collort can be estimated using an appropriate sex ratio at"Ibirth.The projected population under age five can then be determined simplyMass.:3 N. Keyfitz) Introduction to the HAthemntics of Population (Reading,Addison-Wesley, 1968) pp. 27-37.III1II,,I"'- 3 -/1I'I!jI

. ,.I', I,I! / y.1/applying survival ratios to the estimated female Bnd male birth collorts.The final stepin/the projection procedure involves an adjustment of the pro-jected age distributions for net migration.which there ilre several techniques.upon net migration ratios.i'cohort of women expose.d continuously to the fertility schedule underlyingthiS particular t tal fertility rate would produce ultimately an averag ofThis represents another s ep forThe method chosen [or this report is based2,1,6 children, allowing for the effect of female mortality.These ratios represent the proportionate change incohort size attributable to net migration during the projection period.I,The past 15years have witnessed a considerable reduction in the level of American fer-Theytility, including the level of Delaware fertility.If the pr sent trend con-nrc applied directly to the age and sex cohorts in the projected populationtinues at least for the immediate future, then the United States \ ]ill convergeto obtain the projected age' distributions adjusted for net migration.to a replacement population.An initial age distribution combined with a mechanically simple procedurewill not produce a population projection.Certain assumptions about the be-havior f fertility, mortality, and migration during the projection period!.ing national birth expectations indicates that the average woman just beginningSher reproductive career anticipates a completed family size of 2.30 children.I\.!Since Delaware' approximates the United States in reproductive behavior thet.i:,.must be made before any projection can be assembled.These assumptions are2.30 fi&ure \7as assumed to be the 1990 Delm·tare total fertility rate.hcentrjll to a projection, because they determine the form that projection \villtake.Different assumptions will produce different projections, given the sameEvi.dence assembled by the Census Bureau concern-Annualbirth rates by age of mother \vere constructed for 1990, llsing the assumed total fertility rate and the ge structure of Delaware fertility for the periodI"tIinitiai age distribution.The credibility o[ a population projection dependsupon the plausibility o[ each assumption at a given point in time.If the as-srnnptions are not plausible at this point in time, then the projection willfind difficulty gaining acceptance, even though the passage of time may show":itfrom 1969 to 1971. 6 Fertility schedules were then constructed by linear in-t{'\.III:Itorpolation for .;!ach quinquennium fro n 1970 to 1990.These schedules and thecorresponding total fertility rates are shown in table 3. This explains thefertilityasswnption.The next assumption concerns mortality.Ithe assumptions to have been correct.The p pulation projections presentedin this report were prepared under the following set of assumptions.The firstI("assumption concerns fertility.j.The total fertility rate measures the average number of children everborn to \oJomC'n \vl1o survive the childbearing y0ars.4The DC!Ia\ are total. for-I(IItility rate for the period from 1969 to 1971\WS2.46.This means that a1iII4G. Barclay, Techniques oL.,PoEulntion Analysis (NC\v York:1958), pp. 52-53.4Hiley,ISU. S. Bureau of he Census, Current population Reports, Series P-20No. 248, "Birth Expectations and FCl:tiUty: June 1972,11 p. 1.6The original fe1:tility f;chcdulc \vas (lssemblcd for New Castle County,Delaware, w:;ing birth registration elata classif.ied by age o[ mother for thoperiod from 1969 to 1971. These data \,Iere provided by the Cl'nsus anct D.:ttnSystem, Division of Urban Affairs, University of Delaware. Tllo fertilityschedule for cw Castle County was converted to a Delaware SCllCdulc by assuming that both rCf ions have- the sume age SITncture of ferLility (a very plausible assumption) tint! tht'n adjusting the county sched\lle to the- estim.:1tcd 1969 .1971 De1m.;ure- total fertility rate.I!III- 5 -l

. ". w.Icontinuous improvements in disease control technology and preventive med-"Jlcinc Ilave been responsible for more fhan a century of declining mortality inthe United States.There is no evidence to suggest that· Dela\-lare has not beenn party to these fortunate circumstances.Preliminary 1972 estimates derived{rom information aSsembled by the National Center forItHealt. Statistics place!Ithe Delavlare female expectation of life at birth at 73 years, ·the correspond-ing male figure at 70 years,,l vct·nr th s. 7 mc1the infant mortality rate at 19 per thousandThe scientific community has forecasted further improvementsin disease control technology and preventivemedic nethrough the year 2000,but most experts agree that the incremental change in mortality indices willbe smallpr than before and more difficult to achieve.a smallin reasein tile Delaware expectation of life at birth during the next20 years and a correspondingly small decrease in theThe most recentto 1961.8This statement suggestsDel wareinfan mortalityrate life tables were constructed for the period from 1959Since this period, the general, conditions of mortality have not un-dcrgone a radical transformation.The;e have been significant improvements ateach end of the age spectrum, however, and theseto render useless the Delaware life tables forimp ovementsth are sufficientperiod from 1959 to 1961.Current life tables for the period from 1969 to 1971 are being assembled atthe National Center for health Statistics, but these life tables have not beenpublished./Since1t1Colder lifc tablt 1 current and proes do not represent adequa e Yife tables are not yet available,and the newer ld Delaware mortalityJl c lCthis report were prepared using s andMprojections presented in(he populationassembled a set of regional model lifeCoale and Demeny havelife tahles.11' ddemorrraphers ,vith population researchpopulations to assist t blcs and stablep,9 The standard life tables chosen 1 te informat on.in the presence or incomp eThe expectation ofes at level 23.'·1tmodellifetab.lGS{or Dc 1awnr c arc t h e vd 71 years in the male. the female life table an'[C at birth is 75 years 1n11is 18 per thousand live births. nfant mortality rateThe compOsl.te .life table.change 'in mortality indicesthe type of incrementalThese sta tistics represent'1' ze dur ngthe next several'tvi-ll materl.a.experts have agreedwhich populatl. onfemaleis two years higher in thee expe

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