POPULATIONS BY THE NUMBERS

10,000 yrs ago- 5 million Growing Exponentially1930- 2 billion1975 – 4 billion2011 – 7 billion2050 – 9.5 billion

What does it mean to grow exponentially?

Youtube. The most important video you’ll ever see

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

Population CalculationsGlobal 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%

20-8 OR 20-8 x100

10 1000

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%

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 10

Fig. 11.3, p. 240

<1%

1-1.9%

2-2.9%

3+%

Data notavailable

Annual worldpopulation growth

Population Growth Rate

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

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

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.

New Zealand has a population of 4.3 million people, a TFR of 2.1 and a net migration rate of 2 per 1,000.

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.

The migration rate suggests that

2__ = __ x_ _

1000 4,300,000

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?

T= 70 T= 70 = 350 years

r 0.2/yr

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= 1400

Total number in population = 100,000

= 0.014 = 1.4%

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 2045.

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.

The population of Lower Fremont was 20,000 in 1968. In 2010 the population was 160,000. Assuming the growth is exponential, calculate the average annual percentage rate of population growth since 1968.

2010-1968 = 42 years

The population has doubled 3 times since 1968. 20,000 → 40,000 → 80,000 → 160,000

42/3 = 14 years

T= 70/r and r= 70/t

70/14 = 5%

In 2010, the CBR in East Fremont was 25 and the CDR was 11. Calculate the percentage growth rate of East Fremont in 2010. If the population was 15,000 in 2010, and the population growth rate remains constant, when will the population reach 30,000?

__CBR-CDR__ 14 = 1.4%

10 10

70/1.4 = 50 years

50 years + 2010 = 2060

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 = 0.386 mi2

8,175,113 people = 26,804 people/ mi2

305 mi2

26,804 people x 0.386 mi2 = 10,346 people

1 mi2 1 km2 km2

The population of Atlanta is 420,003 and covers an area of 131 square miles.Calculate the density of the population inin mi2 and km2

420,003 people = 3206 people/ mi2

131 mi2

3206 people x 0.386 mi2

mi2 1 km

= 1238 people/km2

How many times more dense is NYC than ATL?

10,346 people/mi2 = 3.2 times

3,206 people/ mi2

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.

States by density: New Jersey, Rhode Island, Massachusetts

States by population: California, Texas, New YorkCities by population: New York, LA, Chicago

“The Lily Pond Parable” from EcoFuturehttp://www.ecofuture.org/pop/facts/exponential70.html

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.___________________________________________________

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

HOMEWORK:

POPULATION CALCULATIONS