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(a)
16 000
14 000
12 000
10 000
8000
6000
4000
2000
0
-1000
-500
0
500
1000
1500
2000
Year
(b)
10 000
1000
Super-
exponential
growth
100
10
1
0
500
1000
1500
2000
Year
Fig. 7.4
(a)Worldpopulationover3000yearscompiledfromvariousdemographic,historicestimatespresentedina
tablebyCohen(1995)andfutureforecastsfromtheUNPopulationDivisionoftheDepartmentofEconomic
andSocialAfairs(2010).Thethicklinedepictstheactualpopulationuptotheearly21stcentury.Thinlines
depicttheUN'sfuture2010low,mediumandhighprojectionsto2050.(b)Worldpopulationonalogarithmic
scale.Thisindicatestherateofexponentialgrowthvaryingovertime.Astraightlinewouldrepresenta
constantrateofproportionalgrowthanditssteepnessindicatestherateofgrowth.Notethatthegraphisnot
astraightlinebutanupwardcurveinthelate20thcentury,relectingsuper-exponentialgrowthforpartof
thatcentury,afterwhichitbecomeslesssteep,indicatingthatpopulationgrowthisslowingdown.
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