Final answer:
The populations of most developed countries are stable or decreasing due to low birth rates and low death rates. This is a result of the demographic transition in these countries.
Step-by-step explanation:
The populations of most developed countries are stable or decreasing. This is because developed countries tend to have low birth rates and low death rates, resulting in a relatively low net population growth rate. In contrast, developing countries tend to have high birth rates and high death rates, leading to large net growth rates. The demographic transition, which is the process of declining birth rates and death rates in developed countries, is a major factor contributing to the stability or decrease in population.