Over the last 100 years, the world's population has exponentially grown from 1.6 billion people in 1920 to an estimated 7.8 billion people today. The shift has been driven by rising birthrates, improved healthcare, and higher life expectancies in many regions. There has also been significant migration, with many countries seeing an influx of new immigrants.
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### Instruction:
Describe the changes in the world's population over the last 100 years.

### Response:
Over the last 100 years, the world's population has exponentially grown from 1.6 billion people in 1920 to an estimated 7.8 billion people today. The shift has been driven by rising birthrates, improved healthcare, and higher life expectancies in many regions. There has also been significant migration, with many countries seeing an influx of new immigrants.
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The world's population has undergone significant changes over the last 100 years, driven by various factors such as improvements in healthcare, sanitation, and living standards. Here are some key changes in the world's population:

1. **Decline in total population**: The world's population has declined from approximately 3.3 billion in 1920 to around 7.9 billion in 2020. This represents a decline of about 42%.
2. **Rapid urbanization**: The global population has grown from approximately 1.6 billion in 1920 to around 4.2 billion in 2020, with urbanization rates increasing from 13% to 45% over the same period.
3. **Aging population**: The global population is aging, with the proportion of people aged 65 and over increasing from 1.1% in 1920 to 14.5% in 2020.
4. **Decline in fertility rates**: Fertility rates have declined significantly over the past century, from an average of 5.2 children per woman in 1920 to around 2.1 children per woman in 2020. This decline is largely due to improvements in education and family planning.
5. **Increased life expectancy**: The global average life expectancy has increased from approximately 34 years in 1920 to around 72 years in 2020.
6. **Shift from rural to urban populations**: The global population is now more urbanized, with people moving from rural areas to cities in search of better living and working conditions.
7. **Growing income inequality**: Despite population growth, income inequality has increased in many parts of the world, with a widening gap between the rich and the poor.

Some key statistics to illustrate these changes include:

* Total population: 3.3 billion (1920) to 7.9 billion (2020)
* Urban population: 13% (1920) to 45% (2020)
* Fertility rate (average): 5.2 children per woman (1920) to 2.1 children per woman (2020)
* Life expectancy: 34 years (1920) to 72 years (2020)

Overall, the world's population has experienced significant changes over the last 100 years, driven by advances in healthcare, sanitation, and living standards, as well as shifts in population demographics.