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**POPULATIONS BY THE NUMBERS**

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10,000 yrs ago- 5 million Growing Exponentially billion 1975 – 4 billion 2011 – 7 billion 2050 – 9.5 billion

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**What does it mean to grow exponentially?**

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Anyone who believes exponential growth can go on forever in a finite world is either a madman or an economist" " --Kenneth Boulding

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**Population Calculations**

Global population growth rate = CBR-CDR 10 If there were 20 people born per 1,000 people and 8 deaths per 1,000, the global population growth rate would be 1.2% OR x100 In 2011, the population growth rate of the …. world was 1.09% Zimbabwe = 4.3% Japan = -0.1% US = 0.9% China= 0.5% India = 1.3%

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To calculate the population growth rate for a single nation, we take immigration and emigration into account. Nat. pop = (CBR + immigr) – (CDR+ emigr) growth rate

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**Population Growth Rate**

Annual world population growth <1% 1-1.9% 2-2.9% 3+% Data not available Fig. 11.3, p. 240

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**Doubling Time and the Rule of 70**

If we know the growth rate of a population and assume that growth rate is constant, we can calculate the number of years it takes for a population to double. Rule-of-70 - way to calculate the approximate number of years it takes for the level of a population growing at a constant rate to double. States that the approximate number of years n for a variable growing at the constant growth rate of r percent, to double is: n = 70/r

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For example, a city with an annual population growth rate of 5% will double its population in approximately 14 years. 70 =14 5 If the growth rate were 7%, it would double its population in approximately ? years. 10

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Remember that a population growing at 2 percent per year, regardless of the size will double in 35 years. Whether the population is 500,000 or 50,000, it will still double in the same amount of time. It is almost certain that the Earth’s population will not double again. Most demographers believe that the human population will be somewhere between 8.1 billion and 9.6 billion in 2050 and stabilize by 2100.

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**New Zealand has a population of 4. 3. million people, a TFR of 2**

New Zealand has a population of million people, a TFR of 2.1 and a net migration rate of 2 per 1, How many people will New Zealand gain next year as a result of immigration? (assume the TFR and net migrations stays the same) Net migration = # of immigrants rate # of people in pop A TFR of 2.1 for a developed country suggests that the country is at replacement-level fertility and thus the population is stable.

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**The migration rate suggests that**

2__ = __ x_ _ ,300,000 So, X= 8,600 people/year Since there is no growth due to biological replacement and a net migration of 8,600 people, the rate of increase is 8,600 people/year = 0.2% 4,300,000 people How many years will it take the population to double at this rate?

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T= T= = 350 years r /yr

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A metropolitan region of 100,000 people has 2,000 births, 500 deaths, 200 emigrants, and 100 immigrants over a 1 year period. Calculate its population growth rate. Net increase = 2,100 Net decrease= 700 Total change in population= Total number in population = 100,000 = = 1.4%

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**In 2010, the population of Upper Fremont was 200,000 and growing at a rate of 2% each year.**

If the rate of population growth remains constant, calculate the population in Determine the doubling time of the population by dividing 70 by 2 to get 35 years. Since one 35-year period passes between 2010 and 2045, the population would have doubled once from 200,000 to 400,000.

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**The population of Lower Fremont was 20,000 in 1968**

The population of Lower Fremont was 20,000 in In 2010 the population was 160,000. Assuming the growth is exponential, calculate the average annual percentage rate of population growth since 1968. = 42 years The population has doubled 3 times since ,000 → 40,000 → 80,000 → 160,000 42/3 = 14 years T= 70/r and r= 70/t 70/14 = 5%

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**In 2010, the CBR in East Fremont was 25 and the CDR was 11**

In 2010, the CBR in East Fremont was 25 and the CDR was 11. Calculate the percentage growth rate of East Fremont in If the population was 15,000 in 2010, and the population growth rate remains constant, when will the population reach 30,000? __CBR-CDR__ = 1.4% 70/1.4 = 50 years 50 years = 2060

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**Population Density New York City has 8,175,113 people within 305 mi2.**

Calculate the density of the population in mi2 and km2. 1 km2 = mi2 8,175,113 people = 26,804 people/ mi2 305 mi2 26,804 people x mi2 = 10,346 people 1 mi km km2

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**The population of Atlanta is 420,003 and covers an area of 131 square miles.**

Calculate the density of the population in in mi2 and km2 420,003 people = people/ mi2 131 mi2 3206 people x mi2 mi km = 1238 people/km2

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**How many times more dense is NYC than ATL?**

10,346 people/mi2 = 3.2 times 3,206 people/ mi2

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**The tiny country of Monaco has the world's highest population density**

The tiny country of Monaco has the world's highest population density. With an area of 3/4 of a square mile and a total population of 32,000, Monaco has a density of almost 43,000 people per square mile. However, since Monaco and other microstates have very high densities due to their extremely small size, Bangladesh is often considered the most densely populated country, with more than 2,200 people per square mile.

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States by density: New Jersey, Rhode Island, Massachusetts States by population: California, Texas, New York Cities by population: New York, LA, Chicago

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**“The Lily Pond Parable” from EcoFuture **

1. If a pond lily population doubles every day, and it takes 30 days to completely cover a pond, on what day will the pond be ¼ covered? 2. If a pond lily population doubles every day, and it takes 30 days to completely cover a pond, on what day will the pond be ½ covered? 3. Does the size of the pond make a difference? 4. What kind of environmental consequences can be expected as the 30th day approaches? 5. What will begin to happen at one minute past the 30th day? 6. At what point (what day) would preventative action become necessary to prevent unpleasant events? Explain your reasoning. ___________________________________________________

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**Try these for practice…**

A. The CBR of a country is 35 and the CDR is 8. Calculate the population growth rate. 2.7% B. The population of a city is growing at a rate of 1.7%. It currently has 100,000 people. What will the population be next year? 101,700 C. A small country of 600,000 people has 15,000 immigrants and 2,500 emigrants. They also experience 8,000 deaths and 5,500 births. What is the growth rate of this country? 1.67% D. How long will it take a population to double if the growth rate is 1.1% 63.64 years

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**HOMEWORK: POPULATION CALCULATIONS**

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