AP Environmental Science

Answer: D - All of the above. The main reasons why crude death rates have decreased for the human population are improvements in medicine and public health, better nutrition, and improvements in water supply, sanitation, and hygiene.

Key Takeaway: The crude death rate is the total number of deaths per year per 1,000 people. Interestingly, the world’s rampant population growth over the last 100 years is mostly due to a huge decline in the crude death rate of the population and has very little to do with actual birth rates. Improvements in medicine and public health, better nutrition, and improvements in water supply, sanitation, and hygiene have allowed us to reach older ages, thus greatly reducing the crude death rate.