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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Over the last 100 years, the world's population has undergone significant changes, driven by various factors such as improvements in healthcare, economic growth, and technological advancements. Here's a brief overview of the major shifts:

**Early 20th century (1900s-1940s):**

* The world's population was approximately 1.5 billion, with Europe and Asia accounting for around 60% of the total.
* The population growth rate was relatively slow, with an average annual growth rate of 0.1%.
* The population was mainly concentrated in rural areas, with urbanization rates low.

**Post-WWII (1945-1960s):**

* The population began to grow rapidly, driven by improved healthcare, sanitation, and living standards.
* The European population grew from 400 million to 1 billion, while the Asian population grew from 500 million to 1.5 billion.
* The population in Africa and Latin America also started to increase, driven by economic growth and migration.

**1960s-1980s:**

* The population growth rate accelerated, reaching an average annual growth rate of 1.3%.
* The global population reached 2.5 billion, with Asia accounting for 40% of the total.
* Urbanization rates began to rise, with cities like Tokyo, New York, and London becoming hubs for population growth.

**1990s-2000s:**

* The population growth rate slowed down, reaching an average annual growth rate of 1.1%.
* The global population reached 6.9 billion, with Asia accounting for 60% of the total.
* The population in Africa and Latin America continued to grow, driven by economic development and migration.

**2010s-present:**

* The population growth rate has declined further, reaching an average annual growth rate of 0.8%.
* The global population reached 7.9 billion, with Asia accounting for 70% of the total.
* The population in Africa and Latin America has slowed down, but is still growing due to high birth rates and limited access to family planning resources.

**Key drivers of population growth:**

1. **Improved healthcare**: Advances in medicine and public health have increased life expectancy and reduced mortality rates, leading to an increase in population.
2. **Economic growth**: As countries have experienced rapid economic growth, more people have been able to afford to have children.
3. **Urbanization**: As cities have become hubs for economic activity, more people have moved to urban areas, leading to increased population growth.
4. **Migration**: People have been migrating from rural areas to cities, contributing to population growth in urban areas.

**Key drivers of population decline:**

1. **Decline in fertility rates**: Many countries have experienced declining fertility rates, leading to a decrease in the number of births.
2. **Aging population**: As people live longer, the number of elderly individuals increases, leading to a decrease in the number of young people entering the workforce.
3. **Low birth rates**: In some countries, low birth rates have led to a decrease in the number of births, contributing to a decline in population.

Overall, the world's population has undergone significant changes over the last 100 years, driven by a combination of factors. While the population has grown rapidly in the past, it has started to decline in recent years due to declining fertility rates and aging populations.