Demographic math Two things you will be able to do at the end of this lesson: Calculate a population’s doubling time Predict future population size Please get out a calculator Doubling time Formula: Time =70 r r= growth rate Example: a country is growing at 2% a year. In how many years will the county’s population double? Practice The Ivory Coast is growing at 3.8% each year. In how many years will it double? China is growing at 1.2%. In what year will China’s population be double what it is today? Calculating future population size A = Pert A = future population size P = current population size Constant e = 2.72 Growth rate r reported as percent of percent T = time A = Pert Try one! The US population this year is 306 million and our growth rate is .6%. How large will the population be in 2050? Try another one! The world’s population is about 677 million and our growth rate is 1.2%. Assuming the rate stays constant, how big will the population be by 2050? By 2100? Check for understanding What two calculations did you just learn how to do? What can you use A = Pert for? Which equation is simpler? What is the common mistake that is made in the A = Pert formula?