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 urbanization. Here are some key changes that have occurred:

1. **Population growth rate:** The world's population has grown from approximately 1.6 billion in 1920 to 7.9 billion in 2020, an increase of about 384% over the last century. This growth rate has been accelerating, with the global population projected to reach 9.7 billion by 2050 and 11.2 billion by 2100.

2. **Age structure:** The age structure of the global population has also changed. In 1920, the median age was around 31 years, while in 2020, it had risen to 37 years. The proportion of the population aged 65 and older has also increased, from around 1.5% in 1920 to 4.3% in 2020.

3. **Urbanization:** The rate of urbanization has been rapid, with the global urban population growing from around 1.5 billion in 1960 to over 4.2 billion in 2020. This has led to significant changes in the way people live, work, and interact with one another.

4. **Migration:** Migration has played a significant role in shaping the global population, with millions of people moving from rural areas to urban centers in search of work, better living conditions, and education.

5. **Demographic changes:** Changes in fertility rates and mortality rates have also influenced population growth. For example, the global fertility rate has declined from 5.0 children per woman in 1960 to 2.4 children per woman in 2020, while the mortality rate has increased from 4.0 deaths per 1,000 population in 1960 to 7.1 deaths per 1,000 population in 2020.

6. **Regional variations:** The population growth and demographic changes have varied significantly across regions. For example, some countries in East Asia, such as China and Japan, have experienced rapid population growth, while others, such as Scandinavian countries, have had slower growth rates.

In summary, the world's population has undergone significant changes over the last 100 years, driven by a combination of factors such as improvements in healthcare, economic growth, and urbanization. These changes have shaped the demographics of the world, with significant implications for global development, poverty reduction, and sustainable living.

**Sources:**

* United Nations Department of Economic and Social Affairs (2020). World Population Prospects 2020.
* World Bank (2020). World Development Indicators.
* Population Reference Bureau (2020). World Population Data Bank.