The population changes in Argentina, Brazil, and Saudi Arabia between 1950 and 2000 can be attributed to several key factors, including fertility rates, mortality rates, migration patterns, economic development, and government policies. Here’s a detailed look at each country:

Argentina

1. Fertility Rates: Argentina experienced a decline in fertility rates over the period. In the 1950s, the total fertility rate was relatively high, but it began to decrease in the subsequent decades due to urbanization, increased education levels, and changes in societal norms regarding family size.
2. Mortality Rates: There was a significant decrease in mortality rates, particularly infant mortality, due to improvements in healthcare, sanitation, and living standards. This led to an increase in life expectancy.
3. Migration: Argentina has historically been a destination for immigrants, particularly from Europe and neighboring Latin American countries. However, immigration rates slowed in the latter half of the 20th century. There was also some emigration, particularly during periods of economic and political instability.
4. Economic Factors: Economic conditions, including periods of economic growth and recession, influenced population growth. Economic instability, especially during the 1980s, may have contributed to lower birth rates and higher emigration.
5. Government Policies: Policies related to healthcare, education, and social services impacted population growth. For example, improved access to education and family planning services contributed to the decline in fertility rates.

Brazil

1. Fertility Rates: Brazil saw a dramatic decline in fertility rates from the 1950s to 2000. In the 1950s, the total fertility rate was above 6 children per woman, but by 2000, it had dropped to around 2.3 children per woman. This decline was influenced by urbanization, increased access to contraception, higher levels of female education, and changing social norms.
2. Mortality Rates: Brazil also experienced a decline in mortality rates due to advancements in healthcare, better nutrition, and improved living conditions. This led to a significant increase in life expectancy.
3. Migration: Internal migration played a significant role in Brazil’s population changes. Large numbers of people moved from rural areas to urban centers, particularly to cities like São Paulo and Rio de Janeiro, in search of better economic opportunities. International migration had less impact compared to internal migration.
4. Economic Development: Brazil’s economic development, especially industrialization and urbanization, influenced population growth. Economic booms in certain periods, like the 1970s, led to population growth in urban areas, while economic crises impacted migration and fertility patterns.
5. Government Policies: Government investments in healthcare and education, as well as policies promoting economic development, contributed to population changes. Family planning programs also played a role in reducing fertility rates.

Saudi Arabia

1. Fertility Rates: Saudi Arabia maintained high fertility rates throughout the period, although there was a slight decline towards the end of the century. Traditional values and norms, coupled with limited access to contraception in the earlier decades, contributed to high fertility.
2. Mortality Rates: The country saw a significant reduction in mortality rates, particularly infant and child mortality, due to substantial improvements in healthcare infrastructure, better nutrition, and overall living conditions. Life expectancy increased as a result.
3. Migration: Saudi Arabia experienced significant immigration, particularly of foreign workers, starting in the 1970s due to the oil boom. This influx of foreign laborers greatly influenced the population size and demographics. Conversely, there was relatively little emigration of Saudi nationals.
4. Economic Factors: The discovery of oil and the subsequent economic boom in the 1970s had a profound impact on Saudi Arabia’s population growth. The wealth generated from oil exports led to rapid modernization, urbanization, and a substantial influx of foreign workers.
5. Government Policies: The Saudi government’s investments in healthcare, education, and infrastructure greatly improved living standards and reduced mortality rates. Policies promoting large families and the limited availability of family planning services in earlier decades contributed to high fertility rates.