Final answer:
Estimating the population for 2021 requires extrapolation from past data, but the provided data is insufficient to make a direct calculation.
Step-by-step explanation:
To estimate the population of a city in 2021, we need to analyze the given data and possibly use a method of extrapolation. However, the raw data provided does not include specific figures for the years post-2000 that can be used to directly calculate or clearly estimate the population for the year 2021. Since there is no clear pattern in the numbers given and no indication of a rate of growth or decline that can be applied, and since historical census data typically requires a trend analysis or a mathematical model to make future predictions, professional assistance from a statistician or the use of demographic software might be required for an accurate forecast.