Why is the population in Northern and Southern Europe aging?

What is the answer

Northern and Southern Europes population is ageing because of rapidly declining fertility rates, a jump in life expectancy and what is the biggest factor, people are immigrating, Romania a Southeastern country has one of the highest rate of people migrating away.

Northern and Southern Europes population is ageing because of rapidly declining fertility rates, a jump in life expectancy and what is the biggest factor, people are immigrating, Romania a Southeastern country has one of the highest rate of people migrating away