Calculate the average rate of change of the emigrant stock for the years 2004-2020. Calculate the chain index numbers. In which year was the stock of migrants the lowest, and in which year the highest? In which year was the annual rate of growth the lowest, and in which year the highest? Knowing that the stock of emigrants in 2020 was estimated at 2.239 million, assess the number of emigrants in 2021 (extrapolating the average rate of change for 2004-2020)