Why is World Population Increasing? Chapter 2 Key Issue 2 Why is World Population Increasing?

Big Question What is natural increase rate (NIR) and how is it calculated? Describe the trend in the natural increase rate of population over the last 117 years. How does NIR, life expectancy, CBR, and CDR vary around the world? What are some reasons why each one varies?

Key Terms Natural Increase Rate (NIR) Doubling Time Life Expectancy Crude Birth Rate (CBR) Crude Death Rate (CDR)

Natural Increase Every year, the Earth’s population grows by about 75-85 million Natural Increase Rate (NRI) is the percentage by which a population grows in a year…excluding migration Birth Rate – Death Rate = NIR Example is Taiwan 8.97 births (per 1,000 people) – 6.87 deaths (per 1,000 people) = 2.10 NIR This century, the world’s NIR has been 1.2% (7,300,000,000 X .012 = 84,000,000 per year)

Natural Increase NIR was around 0 for most of human history (deaths and births nearly equal) Second half of 1900s saw the highest NIRs ever (2.2 in 1963) Humanity took until 1804 to reach its first billion and until 1927 to reach 2 billion After that the population began to grow exponentially (1960 = 3 billion, 1974 = 4 billion, 1987 = 5 billion, 1999 = 6 billion, 2011 = 7 billion)

Regional Variations in NIR NIR also varies greatly across the planet Developing countries have much higher NIR than developed ones Example – 2.0 or greater in Sub-Saharan Africa (31.79 in Zambia and -2.20 in Greece) This means the bulk of birth on Earth are in places that are least able to sustain them

Doubling Time NIR affects doubling time, the rate at which the population doubles At the current rate, the population of the planet will double around 2065 and by 2100 will be 24 billion Doubling time determine by the formula: 70/Rate of Growth (R) = Doubling Time (DT) ex. 70/1.2 = 58.33

Life Expectancy One thing that has a major effect on NIR is life expectancy Life expectancy is the average number of years an individual can expect to live, given current conditions (U.S. 1900 = 46/48, 1925 = 56/58, 1950 = 66/71, 1975 = 69/77, 2000 = 74/80, 2016 = 79/83) Life expectancy varies wildly across the world (highest in 2015 Japan = 81/87 and lowest in 2015 Sierra Leone = 49/51)

Birth and Death Rates Population increases in areas that have more births than deaths and decreases in areas that have more deaths than births. Migration also has an effect (chapter 3)

Birth and Death Rates Fertility is measured by the crude birth rate (CBR) is the total number of live births every year for every 1,000 people alive (ex. CBR of 20 means 20 babies for 1,000 people) Map of CBR looks very similar to that of NIR, highest CBRs are in Sub-Saharan Africa and lowest in Europe

Birth and Death Rates Mortality is measure by the crude death rate (CDR) is the total number of deaths every year for every 1,000 people alive Combined CDR is actually lower in developing countries than developed ones (ex. CDR of Germany is same as Rwanda and U.S. is higher than India These differences can be explained because different countries are in different stages of development which affects the CDR

Big Question & Key Terms What is natural increase rate (NIR) and how is it calculated? Describe the trend in the natural increase rate of population over the last 117 years. How does NIR, life expectancy, CBR, and CDR vary around the world? What are some reasons why each one varies? Natural Increase Rate (NIR) Doubling Time Life Expectancy Crude Birth Rate (CBR) Crude Death Rate (CDR)