Chapter 2 Population Growth to the year2000

Chapter 2

Population Growthto the year 2000

Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Trends in Population Growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......29The Demographic Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......31Projections of World Population Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....33Sources and Bases of Population Projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......34The Built-in Momentum of Population Growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .....36Technical Note A: Projections of Populaticn Growth. . . . . . . . . . . . . . . . . . . . . . . . . . .. .....39Technical Note B: Exponential Growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......39Chapter 2 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......40

LIST OF TABLES

Table No. Page4. Selected Population Data for the 25 Most Populous LDCs. . . . . . . . . . . . . . . . . . . . . .......305. Selected Socioeconomic and Quality of Life Indicators for the 25 Most Populous

LDCs and Selected MDCs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......306. Alternative Projections of Population in 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ....34

LIST OF FIGURES

Figure No. Page4. Comparisons of the Demographic Transition in LDCs and MDCs. . . . . . . . . . . . . . .......325. World Population Growth From 8000 B.C. to 2000 A. D. . . . . . . . . . . . . . . . . . . . . . . .......366A. Age-Sex Composition of More Developed and Less Developed Regions, 1980

and 2000: Medium Series Projection. . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . .376B. Estimated World Population Growth, 1981-2000-2050. . . . . . . . . . . . . . . . . . . . . .......38

Chapter 2

Population Growth to the Year 2000

Abstract

Rapidly declining death rates combined with continuing high birth rates areproducing unprecedented world population growth, some 92 percent of which isoccurring in less developed countries (LDCs). The current world population of4.4 billion is projected to reach about 6.2 billion (range: 5.9 billion to 6.5 billion) in2000. Eighty million people are being added to the world annually; this number isexpected to rise to 9S million per year by 2OOO [range: TO million to 120 million).Growth will be greatest in Africa, Latin America, and Asia. Three quarters of thisgrowth is expected to take place in 18 countries (listed by the magnitude of theirprojected growth): India, China, Brazil, Nigeria, Indonesia, Bangladesh, Pakistan,Mexico, Philippines, Thailand, Vietnam, Turkey, Iran, E~pt, Ethiopia, Burma,South Africa, and Zaire. At current rates of growth, many LDCs will double theirpopulations within 25 years. The difference between the low and high projec-tions for the year 2000 is roughly three times the size of the current U.S. popula-tion. The United States is expected to grow from today’s 226 million to 260 millionin 2000, and 290 million in 2050, but to fall from 4.9 percent of the world’s popu-lation today to 4.0 percent in 2000, and 3.5 percent in 2050. The impact of globalpopulation growth on the united States will thus be greatest from beyond itsborders.

The demographic transition from high to low birthrates experienced earlier bymore developed countries (MDCs) is taking place in LDCs under very differentconditions: death rates have declined at a more rapid pace; LDCs have far greatermomentum of population growth because large proportions of their populationsare reaching reproductive age; international migration Can no longer serve as anoutlet for rapidly growing populations; LDCs have more limited development op-portunities than did MDCs in the past, and LDCs have higher levels of unemploy-ment that were experienced earlier in MDCs. LDCs do have three major new ad-vantages, however: many LDC governments are taking direct actions to reducebirth rates; highly effective fertility planning methods are now available; and theinternational transfer of appropriate knowledge and technology is now orga-nized.

Trends in population growth

29

30 • World Population and Fertility Planning Technologies: The Next 20 Years

ized nations. This historic transition from highto low rates, which began in western Europesome 200 years ago, combined with the indus-trial revolution to sharply divide the world intoone-quarter rich and three-quarters poor. Anumber of terms—more and less developed; de-veloped and developing; North and South; First,Second, and Third Worlds; industrialized andunderdeveloped—describe this division. Thisreport uses those terms most commonly used byinternational agencies: more developed coun-tries and less developed countries.

Although the dichotomy is real, the termsoversimplify. The two groups of nations arevastly different in terms of income, health, edu-cation, and rates of natural increase, but dif-ferences within each group are also wide, asshown in tables 4 and 5. Awareness of the het-erogeneity and individuality of LDCs is vital tounderstanding their levels of development andpopulation growth.

Table 4.—Selected Population Data forthe 25 Most Populous LDCs

(Medium variant)population 1981 1981(millions) rate of doubling

Country 1981 2000 natural increase t i m ea

China . . . . . . .India . . . . . . . . . .Indonesia . . . . . .Brazil . . . . . . . . .Bangladesh . . . .

Pakistan . . . . . . .Nigeria . .Mexico . . . . . . . .Vietnam . . . . . . .Philippines. . . . .

Thailand . . . . . . .Turkey. . . . . . . . .Egypt . . . . . . . . .Iran . . . . . . . . . . .South Korea. . . .

Burma. . . . . . . .Ethiopia . . . . . . .South Afr ica . .Zaire . . . . . . . . . .Colombia . . . . . .

Argentina . . . . . .Afghanistan . . . .Morocco . . . . . . .Algeria . . . . . . . .Sudan . . . . . . . . .

All LDCs . . . . . . .All MDCs . . . . . .World . . . . . . . . .

969710155130

91

8580725453

4946433939

3633302928

2723211919

3,3571,1384,495

1,1901,040

221212153

145149132

7983

766 9656551

5555484642

3337363631

4,9261,2726,199

0.8 592.1 332.0 352.4 292.6 27

2.8 253.2 222.5 282.8 252.4 29

2.0 352.2 323.0 233.0 231.7 41

2.4 292.5 282.4 292.8 252.3 33

1.6 432.7 263.0 233.2 223.1 22

2.1 340.6 1131.7 41

Table 5.—Selected Socioeconomic and Quality ofLife indicators for the 25 Most Populous LDCs and

Selected MDCs1975adult 1981

1978 literacy life 1981G N P rate expectancy infant

Country (dol lars) (percent) (years) m o r t a l i t y

China . . . . . . . . .India . . . . . . . . .Indonesia . . . . .Brazil . . . . . . . . .Bangladesh . . .

Pakistan . . . . . .Nigeria . . . . . . .Mexico. . . . . . . .Vietnam. . . . . . .Philippines . . . .

Thailand . . . . . .Turkey . . . . . . . .Egypt . . . . . . . . .Iran . . . . . . . . . .South Korea . . .

Burma . . . . . . . .Ethiopia. . . . . . .South Africa . . .Zaire . . . . . . . . .Colombia . . . . .

Argentina . . . . .Afghanistan . . .Morocco . . . . . .Algeria. . . . . . . .Sudan . . . . . . . .

United States . .Japan . . . . . . . .UnitedKingdom

. . . . . . . .

230180360

1,57090

230560

1.290’170510

4901,210

4002,160 b

1,160

150120

1,480210850

1,910240670

1,260320

9,5907,2805,0308,260

685250

55564674767373

133127

aNumbe o yr f ears to double population (at current growth rate)

SOURCE: U. N., 1979-World Population Trends and Prospects by Country,1950-2000: Summary Report of the 1978 Assessment for 1981 and2030 population figures; Population Reference Bureau 1981 WorldPopulation Data Sheet for rate of natural Increase and doubling timefigures.

Ch. 2—Popu/ation Growth to the Year 2000 . 31

Following World War 11 the world experi-enced a sudden, sustained drop in deathswhich, combined with little change in births,produced unprecedented growth in numbers ofpeople. Today, about 80 million persons—theequivalent of an additional Mexico or Nigeria—are added to the planet every year (7). By theend of the century, despite reduced birth rates,this annual increase is expected to reach 95million. Most of this increase in numbers is tak-ing place in the LDCs, where expectations of abetter life are also rising.

The timing, intensity, and effects of popula-tion changes have varied greatly among LDCs)

but, beginning with India in the early 1950’s,more than 40 percent of LDC governments havebecome concerned about their rapid growthand its detrimental impact on national develop-ment, and have sought means to reduce theirbirth rates.

Although the most immediate effect of rapidpopulation growth in LDCs has been to limit

their ability to raise living standards, the neg-ative consequences of population growth arenot confined to these countries. MDCs are in-creasingly concerned about their own popula-tion growth. The congressionally establishedCommission on Population Growth and theAmerican Future concluded in 1972 that: “thestabilization of our population could contributesignificantly to the Nation’s ability to solve itsproblems.” National assessments in Great Brit-ain and Japan have reached similar conclusions.A few countries in Europe are worried abouttheir s1OW population growth, but overall thereis growing concern that world population ispushing against the Earth’s carrying capacity.The Independent (Brandt) Commission on Inter-national Development (4) warned of the globalconsequences of population growth and its in-creasingly severe pressure on many basicresources.

The demographic transition

Although the timing of the transition fromhigh to low birth and death rates varies amongcountries, the chronology of the phases issimilar:

1. an early phase of rising growth as deathrates fall and birth rates do not;

2. a peak growth phase as death rates con-tinue to fall and birth rates begin to fall;

3. a falling growth phase as death rates stabi-lize at lower levels and birth rates continueto decline; and

4. a stabilization phase of low, nearly equal,death and birth rates. (See Tech. Note A, ch.4)

Differences in timing have produced muchhigher growth rates at the beginning of thetransition in LDCs than those experienced byM D CS (fig. 4). Conditions in Africa, Asia, andLatin America today therefore differ from thoseof the MDC demographic transition in severalvery important ways:

● Death rates declined much faster in LDCsthan they did earlier in MDCs. The decline in

●

●

annual death rates from 30 to 15 per 1,000population that took 150 years in Great Brit-ain, Sweden, and the United States, tookonly about 35 years in India. Declines inLDC death rates from major causes such ascholera, malaria, and smallpox have beenfacilitated by new large-scale internationaltransfers of health and agricultural tech-nologies from MDCs.

As a result, population growth has been muchmore rapid in LDCs in both rates and ab-solute numbers than it was in MDCs. GreatBritain’s growth rate fell slowly from 1.4 to0.4 percent between 1800 and 1921; the an-nual increase in numbers did not deviategreatly from 200,000. By contrast, India’sannual growth rate rose from about 1.5 to2.5 percent between 1950 and 1970 as itsannual increase in numbers soared fromabout 5 to 11 million in just 20 years.

LDCs have greater momentum of populationgrowth built into their age structures thanMDCs had earlier. Sustained higher birth

32 • World Population and Fertility Planning Technologies: The Next 20 Years

Figure 4.—Comparisons of the Demographic

50

40

30

20

10

0

MDCS

--- Assumed trend in the absence ofWorld Wars I and II

1 1 I I1750 1800 1850 1900 1950 2000

In MDCs death rates declined slowly beginning in the late18th century. Birth rates followed closely. - Popula t iongrowth rates rarely exceeded 1.5 percent per year.

LDCs

Birth rate

In LDCs birth and death rates remained high through thefirst decades of the 20th century. Then death rates began todrop. Birth rates stayed high and populations grew at 2.5,3.0, and 3.5 percent or higher a year. Since the mid-1960’ssome countries’ birth rates have begun to decline.

SOURCE: State Department Bulletin, “The Silent Explosion,” fall 1978.

●

●

●

rates have produced large proportions ofchildren who will soon reach reproductiveage. Thus, even if average family size isreduced dramatically in this generation, na-tional birth rates will fall more slowlybecause such a large proportion of peopleare of reproductive age.International migration can no longer serve asan outlet for rapidly growing populations as itdid for much of Europe. There are no more‘(empty” lands to colonize or to accept greatnumbers of immigrants. Nevertheless, pop-ulation pressures in LDCs and income op-portunities in MDCs are likely to result insizable illegal migration and its attendantproblems as long as rapid populationgrowth in LDCs continues.LDCs have far fewer opportunities fordevelopment than did MDCs. Most LDCshave little unutilized arable land, areunevenly endowed with natural resources,and face stiff competition from MDCs in in-ternational markets for industrial products.LDCs face higher levels of unemploymentthan were experienced earlier in MCs. Theopportunities for employment (or migra-tion) that were available earlier in MDCsare not available in LDCs, where unemploy-ment and underemployment are wide-spread.

In sum, LDCs have not only encountered pop-ulation growth unlike anything in MDC experi-ence, but have fewer opportunities for accom-modating this growth than were available toMDCs a century earlier. They do, however,have three major new developments in theirfavor:

1. Many LDC governments, unlike MDCs earli-er, are taking direct actions to reduce birthrates by utilizing new fertility planning tech-nologies and by other means. Although fam-ily planning programs vary greatly in effortand effects and most governments allocateless than 1 percent of governmental ex-penditures to them, more than 92 percentof the world’s population live in countrieswhose governments provide some form offamily planning services for their people.(See ch. 7.)

Ch. 2—Popu/ation Growth to the Year 2000 ● 33

Z. There are more effective technologies for theplanning of births than existed in 1800 oreven 1950. These technologies—the pill,IUD, and new voluntary sterilization tech-niques–have replaced less effective meth-ods in MDCs and are beginning to be usedin LDCs. (Technological development isnow lagging, however; although concertedresearch efforts to develop better con-traceptive technologies increased appre-ciably during the 1960’s, financial supportfor such efforts has fallen in real purchasingpower since 1970.) (See ch. 6.)

3. international transfer of knowledge and tech-nologies to reduce birth rates is now orga-nized. The proportion of total internationaldevelopment assistance devoted to popula-

tion activities rose from virtually none in1960 to 2 percent in 1979. MDCs now pro-vide about $450 million annually for popu-lation assistance. (See ch. 9.)

This assessment focuses on policies of the U.S.Government now and during the next 20 years,which will be a pivotal period in global popula-tion history. LDCs receive greatest considera-tion because problems arising from rapid pop-ulation growth are particularly acute in thesecountries and because their population growthbetween 1980 and 2000 will account for morethan 90 percent of the rise in world numbers.How fertility can be changed takes precedencebecause it is the most viable option for countriesthat wish to lower population growth rates.

Projections of world population growth

The size of world population during the next20 years can be predicted with greater certaintythan most future events because about 60 per-cent of the people who will be on Earth in 2000A.D. are already here, and—barring a possibleglobal nuclear catastrophe or unexpected greatepidemic or famine—experts differ little on howmany will die in the coming two decades. Theuncertainties lie in how many people will beborn. Their numbers will depend to a great ex-tent on what the LDCs do to modify their na-tional birth rates. There is a consensus thatpopulation growth has such a powerful, built-inmomentum that actions taken or not taken nowwill determine the size of world populations farinto the future.

World population is projected to grow froman estimated 4.5 billion in mid-1981 to 6.2 billion(between 5.9 and 6.5 billion; much will dependupon the rates at which fertility declines) inmid-2000. Despite decreasing growth rates, thetotal number of persons added to the world’spopulation each year is expected to increasefrom some 80 million in 1981 to about 95 million(between 70 and 120 million) in 2000. Thisgrowth will be distributed very unevenly amongdifferent regions and countries. Close to 92 per-cent is expected to occur in LDCs, cutting theMDC proportion of world population from 26

percent in 1980 to 21 percent in 2000 (and theU.S. proportion from 4.9 to 4.0 percent).

The LDCs differ greatly in population size andgrowth both by individual countries and by geo-graphic regions. Growth will be greatest, ac-cording to current projections, in Africa (76 per-cent of the 1980 population added in 20 years),Latin America (65 percent), and Asia (43 per-cent), However, more of the increase in absolutenumbers will occur in Asia (63 percent) than inAfrica (22 percent) or in Latin America (15 per-cent), simply because many more people al-

ready live in Asia. Three-quarters of all1980-2000 LDC growth is expected to occur injust 18 countries: India, China, Brazil, Nigeria,Indonesia, Bangladesh, Pakistan, Mexico, Philip-pines, Thailand, Vietnam, Turkey, Iran, Egypt,Ethiopia, Burma, South Africa, and Zaire, listedhere by the magnitude of their projectedgrowth. Much of future world populationgrowth thus depends upon what happens inthese few large countries.

The interval during which some of thesecountries will double their populations, if pres-ent fertility trends continue, is very brief: Kenyamay double the numbers of its people in 18years, India in 33, Bangladesh in 27, and Egvptin 23 (table 4). (See Tech. Note B.)

Sources and bases of population projections

The projections used here are those of theUnited Nations (U.N.), the principal source of in-formation about world population. Its Popula-tion and Statistical Divisions publish currentpopulation, birth, and death data annually andprepare periodic global assessments and projec-tions.

Projections based upon a 1978 assessmentwere published in 1979; revised projectionsbased upon a 1980 assessment were publishedin 1981. The projections include high, medium,and low variants. The medium variant is de-signed to represent likely demographic trendsbased on past demographic changes, expectedsocial and economic progress, ongoing govern-ment population policies, and prevailing publicattitudes toward population issues. The highand low variants are intended to represent theeffects of plausible variations in these factors.

The U.N. projections are similar to those pro-duced by five other major sources (table 6).Each set of projections starts from estimated1975 base populations, fertility rates, and lifeexpectancies. Each uses similar assumptionsabout death rates and assumes no major wars,famines, or epidemics, and all except the U.N.exclude international migration. All depend ondata from individual nations—sources whosefrequency, accuracy, and completeness of infor-mation vary greatly. (See Tech. Note A.)

The projections prepared by the U.S. Bureauof the Census also include high, medium, andlow series, and are based on current levels offertility, development, and family planning; gov-ernment policy on population matters; and ex-perience in countries with similar social, eco-nomic, and political settings. These projectionsassume that fertility will decline more or lesscontinuously throughout the period, that all

Table 6.—Alternative Projections of Population in 2000 (millions)

Source

U.S. Bureau United World University of Harvard Populationof the Census Nations Bank Chicago (6) University (5) Councilc

Region 1980 1979 1979 1977 1977 1981

World:High . . . . . . . . . 6,520 6,508 – 5,974 — 6,353Medium . . . . . . 6,175 6,199 6,004 5,883 5,882Low . . . . . . . . .

—5,799 5,855 – 5,752 — 6,046

MDCsHigh . . . . . . . . . 1,324 1,319 – 1,266 — 1,135Medium . . . . . . 1,272 1,272 1,261a 1,263 1,275a —Low . . . . . . . . . 1,225 1,229 – 1,250 — 1,054

LDCsHigh . . . . . . . . . 5,196 5,189 – 4,706 — 5,218Medium . . . . . . 4,903 4,926 4,743 4,620 4,807 —Low . . . . . . . . . 4,574 4,626 — 4,501 — 4,992

China:High . . . . . . . . . 1,425 1,228 — 1,135 —Medium . . . . . .

—1,284 1,189 1,210 b 1,131 1,129 NA

Low . . . . . . . . . 1,141 1,132 — 1,109 —India

—

High . . . . . . . . . 995 1,105 971 — —Medium . . . . . . 959 1,037 973 951 1,009 NALow . . . . . . . . . 922 983 – 923 —

Ch. 2—Population Growth to the Year 2000 ● 35

countries will have adopted some kind of familyplanning program by 2000, and that the effec-tiveness and coverage of such programs will in-crease.

The World Bank’s single population projectionwas prepared by estimating, for each country,

the year in which fertility would reach replace-ment level. For all countries except those in sub-Saharan Africa, fertility decline toward the re-placement level is assumed to have started in1975 if not before. For the sub-Saharan coun-tries, the declines are expected to begin in1980-85.

The University of Chicago projections also in-clude high, medium, and low variants. The pro-jected fertility rates are based On specified rela-tionships between the rate of fertility declineand the strength of family planning efforts. Thehigh projection assumes that each countrymaintains its present level of family planning ef-fort. The medium projection assumes thatstrong family planning efforts eventually are im-plemented in all nations by the year 2000. Thelow projection assumes that all countries havestrong family planning programs by 1995.

The Harvard University projections assumethat fertility will decline to replacement levelsby 1990-95 in MDCs and by 2000-05 in LDCs.The Population Council projections assume at-tainment of replacement level fertility at vary-ing times from 1980-85 to 2040-45. Differencesamong the six sets of projections summarized intable 6 are mainly in base data used, in assump-tions about future LDC birth rates, and in inter-pretations of incomplete data about China andcentral Africa. Despite these differences, theoutcomes in world, LDC, and MDC populationestimates for 2000 are quite similar among thefirst five. The university scholars and the WorldBank expect slightly less growth in LDCs thando the U.S. Census Bureau and the U.N. Popula-tion Division.

Much of the uncertainty about China shouldbe resolved by its 1982 census and pending im-provements in and availability of its birth,death, and birth planning program data. Mean-while, special population projections for China(l)—based upon China’s new emphasis on theone-child family to achieve population stabiliza-tion by 20()()-come close to the low estimates intable 6.

The U.N. projections have been used as stand-ard reference figures in most of this report buthave been supplemented by new national datawhere available and relevant.

For policy makers concerned with modififyingpopulation growth, the most meaningful popu-lation information is the difference in numbersof people added to the world’s population ifgovernments do or do not take feasible actionsto reduce birth rates in addition to thosealready under way. The actual amount attribut-able to additional governmental actions thatreduce birth rates is neither accurately’ knownnor explicitly stated by most demographic ex-perts who make projections. There is generalagreement, however, that if gotvernments inten-sify current actions to reduce growth rates, thelow variant projection is more Iikely to beachieved. The total difference between the highand low variants is sizable-650 million per-sons—and is equivalent to the addition of threetimes the current U.S. population in just 20years (table 6 and fig. 5).

The tendency of demographers to follow pasttrends and to underestimate changes in birthrates means that the low variant projections for2000 are probably not low’ enough. New infor-mation has already led to downward revisionsof these low variants. The 1980 Census Bureaulow series projection for lvorld population i n2000 was 2-percent lower than in 1977. Some ofthis change in predictions can be attributed togovernmental actions.

36 . World Population and Fertility Planning Technologies: The Next 20 Years

Figure 5.–World Population Growth From 8000 B.C. to 2000 A.D.

A.D. 2000 high variantprojection: 6.5 billion ‘ 6.5

A.D. 2000 medium variant Am \

projection: 6.2 billion

A.D. 2000 low variantprojection: 5.9 billlon I

The difference in numbers of people added to the world’s popula- 1

tion by 2000 will depend to a significant extent on the actionstaken by governments to modify birth rates. The difference be-tween the high and low projections—about 650 million persons—is equivalent to the addition of three times the current U.S.population within 20 years. Close to 92 percent of population W ;

growth projected by 2000 is expected to occur in LDCs.

Chart shows world populationgrowth since 8000 B.C. Ifstretched back all the way tothe beginning—300,000 B.C.—in this scale, the line wouldbe an invisibly thin one start-ing 10 feet 71/2 inches to theleft of the graph

1945.3 billionL2

r 1850 1I 1 billion I I

6000 B.C.5 million

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

The built-in momentum of population growth

Population growth in the next 20 years hasenormous momentum that will affect later pop-ulation size. This momentum comes from thecombination of high fertility and rapidly declin-ing infant mortality in LDCs that followedWorld War II. The result is a subtle, very pow-erful built-in inertia, resulting from the agestructure of LDC populations (fig. 6A).

In LDCs, far more people are in the youngerage groups than in the older ones. Because thenumber of people entering the reproductiveages each year will be more than 150-percentgreater that the number leaving them, the num-ber of births will be greater each year, even if fer-tility rates fall dramatically. Because the younger

age groups will be so much larger than the olderage groups, the number of people being borneach year will be much greater than the num-ber of people dying. Even when fertility ap-proaches replacement levels, the number ofdeaths will not equal births until the largest co-hort of births reaches old age, some 60 yearslater.

In contrast to the LDCs, by 2000 the MDCswill have a very even distribution of populationby age (fig. 6A). The number of people in each5-year age group between birth and 50 yearswill be between 87 and 93 million. Each yearjust as many people will move out of their repro-ductive years as will enter them. With births at

Ch. 2—Popu/ation Growth to the Year 2000 ● 37

Fiaure 6A.—Aae.Sex Composition of More Developed and Less Developed Regions, 1980 and 2000:.g=—. – .Medium Series Projections

A _ - More developed regions

75+

70

60

50

[

Male Female

I I I 1 I I I

Age

75+

— 70

— 60

— 50

— 40

— 30

— 20

— 10

0w

300 260 220 180 140 100 60 20 020 60 100 140 180 220 260 300

Age

— 75+

— 70

— 60

— 50

— 40

— 30

“ 20

— 10

— o300 260 220 180 140 100 60 20 0 20 60 100 140 180 220 260 300 -

MillionsSOURCE: U.S. Bureau of the Census, Illustrative Projections of World Populations to the 21st Century, Special Study Series, table 2, pt. B, p. 23, No. 79,

January 1979.

38 ● World Population and Fertility Planning Technologies: The Next 20 Years

replacement level, approximately the samenumber of children will be born each year. Fur-thermore, because the size of the older agegroups will be about the same as the youngerage groups, the number of children born eachyear will be about the same as the number ofpersons dying each year. By 2000, many MDCsare expected to have achieved populationstabilization—or zero population growth—withlow birth rates equal to low death rates, if theirimmigration is in balance with their emigration,

One effect of the population momentum inLDCs is to foreclose future options if actions arenot taken in time. Frejka and Mauldin (2) con-clude that the range between the high and lowvariants, and thus the range for plausible gov-ernment options for the eventual size of worldpopulation toward the end of the next century,was narrowed by 3 billion people in a singledecade. Taking certain actions to reduce birthrates lowered the plausible upper level; not tak-ing other actions raised the plausible lowerlimit, because by 1980 population momentum

had become a part of the built-in growth projec-tion.

How actions taken now can affect the futuresize of world population is shown in figure 6B.Despite all feasible efforts to reduce birth rates,the world’s population will almost certainly dou-ble from 4.4 billion to well over 8 billion personsin the next 70 years. But if the world insteadchooses a path of high growth by doing nothingfurther to change trends, an additional popula-tion roughly equivalent to that of the entire worldin 1981 will be on Earth in 2050. Most of thesepeople would be born in the LDCs, where theinitial direct impact of their numbers would bemost keenly felt.

The United States is expected to grow from226 million in 1980 to about 260 million in 2000,and to about 290 million in 2050, while at thesame time dropping from 4.9 to 4.0 to 3.5 per-cent of the world’s population. The impact ofglobal population growth on the United Stateswill thus be greatest from beyond its borders.

Figure 6B.–Estimated World Population Growth, 1981-2000-2050(in billions)

1981 2000 2050

6,508 12,403

5,855 8,384

SOURCE: United Nations, 1979, World Population Trends and Prospects by Country, 1950-2000; Summary Report of the 1978Assessment for 1981 and 2000 population figures,

Ch. 2—Popu/arion Growth to the Year 2000 ● 39

The magnitude of growth in many LDCs will capacity and stability of the entire world will bealmost certainly be disruptive within those felt everywhere. What some of those impactscountries but the challenge to the carrying are likely to be is examined next.

Technical Note A: Projections of population growth

and on birth and death rates for the base year. If thesize estimate is in error, the projection will be inac-curate by the amount of error from the beginning.Inaccuracies will be compounded to the extent thatbirth and death rate data are inaccurate. This factoris the most serious problem in projecting populationgrowth rates in LDCs) where data are often of poorquality.

Projections made in prior decades for the year1980 illustrate this problem of poor quality baselinedata. The U.N.’S most recent projection estimatesworld population at 4.43 billion in 1980. In 1973 thisprojection was 4.37 billion (1.3 percent less than the1980 estimate); in 1963 it was 4.33 billion (2.2 percentless); and in 1957 it was 4.22 billion (4.7 percent less).The major factor affecting these projections was theinaccuracy of base data on death rates. The deathrate for 1960-65 was estimated in 1963 to be 15.9 per1)000 for the world and 19.2 for LDCs. Today therespective rates for 1960-65 are estimated to havebeen 14.4 (10 percent less) and 16.8 (12.5 percentless). The decline in death rates was projected fairlyaccurately, but the higher base figures led to lowoverall growth rates. Birth rates were estimatedmore accurately for the base years but were pro-jected to decline more slowly than they actually did,which compensated to some extent for the highdeath rate projections. Based on calculations of errorand estimates of quality of current baseline data, pro-jections for 2000 have an uncertainty range of 10 to20 percent.

Technical Note B: Exponential growth

The concept of exponential growth can be illus- males each woman has since women bear childrentrated by observing, during a certain length of time, and the ratio of males to females is usually close toa theoretical population in which the rate of repro- 1:1). The two females leave four females in the nextduction per individual remains constant. Each female generation, the four leave eight, the eight leave six-on average leaves two females in the next generation. teen, and so forth. If this were a population with an(Population grolvth is measured by the number of fe- age at marriage (generation length) of 20, the popula-

tion would double every 20 years. Because individ-uals in this population are reproducing at a constantrate, the rate at which the population increases de-pends on the number of people at the beginning. Apopulation with 10 females at the beginning in-creases faster than a population with two females atthe beginning even though each is reproducing atthe same rate. This kind of population increase,known as exponential growth, is also referred to asgeometric or logarithmic growth. If exponential

growth were to continue unchecked, the worldwould soon contain more living organisms thanatoms in the universe. The factors that keep thisgrowth in check are the number of deaths in a popu-lation (growth rates slow if death rates rise), the timebetween generations (age at marriage in human pop-ulations), and the number of offspring each couplehas (fertility). (Migration is a factor only for individ-ual countries.)

Chapter 2 References

1. Chen, P., contractor’s report to OTA, 1980.2. Frejka, T., “~$~orld Population Projections: A Con-

cise History, ” Population Council Center forPolicy Studies, Working Paper No. 66, Ne\v York,1981.

~. Futures (h’OUp, “The Impacts of Population(;rowth on Less Developed Countries,” (ITAworking paper, 1980.

4. Independent Commission on International Devel-opment Issues (Winy Brandt, Chairman), Norfh-South: A Program for Sur\~iva/ (Cambridge, Mass.:NI. I.T. Press, 1980).

5. I.ittman, (;., and Key fitz, N., The Next 100 Years,(Mter for Population Studies Working Paper NO.101 (Cambridge, itlass.: Har\’ard LJni\’ersity,1980).

6. Tsui, A. ()., and Bogue, D. J., Population Projec-tions .fbr the World, 1975-2000: Summary Reportof the 1978 Assessment, New York, 1979.

7. United Nations, World Population Trends andProspects by Country, 1950-2000: Summary Re-port cf the 1978 Assessment, Ne\v York, 1979.

8. U.S. Commission on Population Growth and theAmerican Future, “Population Growth and theAnlerican Future” M’ashington, D. C.: Govern-ment Printing Office, 1972).

9. IJ.S. Council on Environmental Quality and De-partment of State (G. O. Barney, Study Director),The Global 2000 Report to the President(Washington, D. C.: Government Printing office,1980).

lo. tJ. S. Department of Commerce, Bureau of theCensus, illustrative Projections of world Popula-tion in the 21st Centurey, Current PopulationReport, Special Study Series P-23, No. 79(Washington, DC.: Goiernrnent Printing Office,1979).

11. , 1980. Re\~ised table to above.12. World Bank Development Economics Depart-

ment, prepared by K, C. Zachariah and Aly ThiV Ll , Popu lat ion Pro ject ions, 1975-2000 and Lon~ Term (Stationary Population)(Jt’ashington, D. C.: ~ToI.]C~ Bank, 1979).