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.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### 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.
assistant

Over the last 100 years, the world's population has undergone significant changes due to various factors such as improvements in healthcare, increased life expectancy, and changes in birth rates. Here's an overview of the changes:

**Early 20th century (1900-1945):**

* The global population was approximately 1.5 billion people.
* The average life expectancy at birth was around 35 years.
* The world experienced a rapid decline in population due to high mortality rates, wars, and diseases such as the Black Death.

**Post-WWII (1945-1964):**

* The population began to recover due to improvements in healthcare, sanitation, and nutrition.
* The average life expectancy at birth increased to around 48 years.
* The world population reached around 2.5 billion people.

**High-growth period (1964-1980):**

* The population experienced rapid growth due to high birth rates, particularly in developing countries.
* The average life expectancy at birth increased to around 55 years.
* The world population reached around 4.2 billion people.

**Decline in high-growth period (1980-2000):**

* The population began to decline due to low birth rates, technological advancements, and the rise of Western societies.
* The average life expectancy at birth decreased to around 59 years.
* The world population reached around 6.3 billion people.

**Stagnation in low-growth period (2000-2019):**

* The population continued to decline due to low birth rates, urbanization, and changes in lifestyle.
* The average life expectancy at birth remained relatively stable at around 68 years.
* The world population reached around 7.7 billion people.

**Recent trends (2019-present):**

* The population has been slowing down due to declining birth rates, increased life expectancy, and urbanization.
* The average life expectancy at birth remains around 72 years.
* The world population is projected to reach around 8.5 billion people by 2050.

Overall, the world's population has grown from approximately 1.5 billion in 1900 to around 8.5 billion today. While the population has experienced significant changes over the last 100 years, it is now growing at a slower rate due to declining birth rates and increasing life expectancy.