Question

1.what could be the reason of increase in life expectancy in a country

2.why per capita income is always taken in dollars ​

Answer 1

During the nineteenth and early twentieth centuries, an increase in life expectancy was driven mainly by improvements in sanitation, housing, and education, causing a steady decline in early and mid-life mortality, which was chiefly due to infections.

Per capita income is counted in dollar rather than rupee because dollar is an officially used currency. Because dollar is regarded as an international medium of exchange so it's better to count per capita income of every nation in dollars rather than their own currency .