There are several reasons why it takes a long time to slow population growth:
1. Social and cultural factors: Changing social norms and cultural attitudes towards family planning and contraception can take time. In some societies, having large families is still seen as a sign of prestige or a cultural norm. It takes time to educate and change these attitudes.
2. Lack of access to contraception: In many parts of the world, especially in developing countries, there is limited access to contraception and family planning services. This can be due to several factors such as cost, availability, and geographic barriers. Improving access to contraception takes time and resources.
3. Lack of education and awareness: Many people are unaware of the consequences of rapid population growth, such as increased strain on resources and environmental degradation. Education and awareness campaigns are necessary to inform individuals and communities about the benefits of family planning.
4. Economic and poverty issues: High poverty rates and lack of economic opportunities can drive people to have larger families, as children can be seen as an economic asset and a source of support for the family. Improving economic conditions and reducing poverty can help alleviate the pressure for larger families.
5. Demographic momentum: Even if the fertility rate decreases, there is often a "demographic momentum" that takes time to slow down population growth. This is because the current large population of reproductive age will continue to have children for several years, even if they have fewer children on average.
Overall, slowing down population growth is a complex issue that requires a multi-faceted approach, involving education, access to contraception, economic development, and changing cultural attitudes. These changes take time to implement and have a significant impact on population growth rates.