Final answer:
The demographic equation is the formula that calculates regional population change by considering births, deaths, and net migration, essential for analyzing the demographic transition stage of a country.
Step-by-step explanation:
The calculation that summarizes the contribution to regional population change by natural change (births minus deaths) and net migration is known as the demographic equation. This formula includes the number of births, the number of deaths, and the net migration (the difference between the number of immigrants and emigrants) to determine the population change over a given time period. It is significant because it helps to calculate a population's growth rate and analyze which stage in the demographic transition model a country is in.