The percentage by which a population grows in a year is called

Net reproductive rate (r) is calculated as: r = (births-deaths)/population size or to get in percentage terms

Explanation:

Net reproductive rate (r) is calculated as: r = (births-deaths)/population size or to get in percentage terms, just multiply by 100. the population is so much bigger, many more individuals are added. If a population grows by a constant percentage per year, this eventually adds up to what we call exponential growth, i expect a thx i explained it really well,see ya stranger bye.