POPULATION GROWTH
Population growth is the change in population over time and can be quantified as the change in the number of individuals in a population per unit of time. Population growth is often expressed as population growth rate, the fractional rate at which the number of individuals in a population increases. However, the most common way to express population growth is as a ratio, not as a rate.
To help understand this, let’s suppose an island has 100 people on January 1 and 101 people 12 months later on December 31. The annual population growth rate would be .01 or 1% . This is calculated by taking the population at the end of the time period (101) minus the population at the beginning of the time period (100) – which equals the population growth, or 1 in our example – divided by the population at the beginning of the time period (100). Thus: 101-100/100 = 1/100 or .01 or 1%.
In our example, the growth ratio would be 1 per 100 population.
A positive growth ratio (or rate) indicates a population is growing, while a negative growth ratio (or rate) means the population is declining.
One intriguing way to look at population growth is using the growth rate to determine “doubling time;” that is, how long it will take a current population to double. This is determined by dividing the growth rate into 70. (The number 70 comes from the natural log of 2, which is .70.)
With a growth rate of 1%, our island population would take 70 years to double. (70/1 = 70)
According to the CIA World Factbook, the current worldwide population growth rate is 1.133% – nearly 80 million humans per year. If current growth continues, we can expect the world's population of 6.8 billion to become 13.6 billion in about 62 years (around 2072). This is calculated by dividing 70 by the world growth rate of 1.133: 70/1.133 = 61.78, which we round off to 62 years.
The world's growth rate as a percentage peaked in 1963 at 2.19% and a doubling time of 35 years. The actual annual growth in the number of humans peaked at 87.5 million per year in 1989, falling to a low of 76.4 million per year in 2002. Since then, it has slowly started to rise again. In 2009, the annual world population growth was between 78 and 80 million. (Source: Wikipedia)
Ten Most Populated Countries (July 2009)
|
Country |
Population |
% of World Population |
| 1 |
People's Republic of China |
1,334,690,000 |
20.0% |
| 2 |
India |
1,173,860,000 |
17.0% |
| 3 |
United States |
308,162,000 |
4.5% |
| 4 |
Indonesia |
231,369,500 |
3.4% |
| 5 |
Brazil |
191,189,000 |
2.8% |
| 6 |
Pakistan |
168,211,500 |
2.5% |
| 7 |
Bangledesh |
162,221,000 |
2.4% |
| 8 |
Nigeria |
154,729,000 |
2.3% |
| 9 |
Russia |
141,901,279 |
2.1% |
| 10 |
Japan |
127,560,000 |
1.9% |
|
TOTAL |
3,993,893,279 |
58.9% |
Source: Wikipedia
WORLD POPULATION GROWTH HISTORICALLY
The worldwide population of humans has been growing steadily since before recorded history. From fewer than 1 million humans around 70,000 BC to the Day of 6 Billion on October 12, 1999, to today’s estimated 6.8 billion humans, we continue to be one of the most prolific species to inhabit Planet Earth. In fact, the number of humans to have ever lived has been estimated at over 100 billion – 15 times the current world population! (see below for links to commentary on how many humans have ever lived.)
Historical Estimates of World Population
| Year |
World Population |
| 70,000 BC |
Less than 1 million |
| 10,000 BC |
1 to 10 million |
| 8000 BC |
5 million |
| 6500 BC |
5 to 10 million |
| 5000 BC |
5 to 20 million |
| 4000 BC |
7 million |
| 3000 BC |
14 million |
| 2000 BC |
27 million |
| 1000 BC |
50 million |
| 500 BC |
100 million |
| 400 BC |
162 million |
| 200 BC |
150 to 231 million |
| 1 AD |
170 to 400 million |
| 200 AD |
190 to 256 million |
| 400 AD |
190 to 206 million |
| 500 AD |
190 to 206 million |
| 600 AD |
200 to 206 million |
| 700 AD |
207 to 210 million |
| 800 AD |
220 to 224 million |
| 900 AD |
226 to 240 million |
| 1000 AD |
254 to 345 million |
| 1100 AD |
301 to 320 million |
| 1200 AD |
360 to 450 million |
| 1300 AD |
360 to 432 million |
| 1400 AD |
350 to 375 million |
| 1500 AD |
425 to 540 million |
| 1600 AD |
545 to 579 million |
| 1650 AD |
470 to 545 million |
| 1700 AD |
600 to 679 million |
| 1750 AD |
629 to 961 million |
| 1800 AD |
813 to 1,125 million |
| 1850 AD |
1,128 to 1,402 million |
| 1900 AD |
1,550 to 1,762 million |
| 1910 AD |
1.75 billion |
| 1920 AD |
1.86 billion |
| 1930 AD |
2.07 billion |
| 1940 AD |
2.3 billion |
| 1950 AD |
2.555 billion |
| 1960 AD |
3.0 billion |
| 1970 AD |
3.712 billion |
| 1980 AD |
4.425 billion |
| 1990 AD |
5.284 billion |
| 2000 AD |
6.092 billion |
| 2010 AD |
6.870 billion |
Source: U.S. Census Bureau
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