EVERYDAY SCIENCE

Detailed explanation-1: -Population change is governed by the balance between birth rates and death rates. If the birth rate stays the same and the death rate decreases, then population numbers will grow.

Detailed explanation-2: -If the birth rate is larger than the death rate, then the population grows. If the death rate is larger than the birth rate, what will happen to the population? The population size will decrease. If the birth and death rates are equal, then the population size will not change.

Detailed explanation-3: -When demographers attempt to forecast changes in the size of a population, they typically focus on four main factors: fertility rates, mortality rates (life expectancy), the initial age profile of the population (whether it is relatively old or relatively young to begin with) and migration.

Detailed explanation-4: -The main components of population change are births, deaths, and migration. “Natural increase” is defined as the difference between live births and deaths. “Net migration” is defined as the difference between the number of people moving into an area and the number of people moving out.

Detailed explanation-5: -And while every population pyramid is unique, most can be categorized into three prototypical shapes: expansive (young and growing), constrictive (elderly and shrinking), and stationary (little or no population growth). Let’s take a deeper dive into the trends these three shapes reveal about a population and its needs.