The table gives the population of Indonesia, in millions, for the second half of the 20th century.

Year ................ Population
1950 ................ 83
1960 ................100
1970 ................ 122
1980 ................ 150
1990 ................ 182
2000 ................ 214

(a) Assuming the population grows at a rate proportional to its size, use the census figures for 1950 and 1960 to predict the population in 1980. Compare with the actual figure.
(b) Use the census figures for 1960 and 1980 to predict the population in 2000. Compare with the actual population.
(c) Use the census figures for 1980 and 2000 to predict the population in 2010 and compare with the actual population of 243 million.
(d) Use the model in part (c) to predict the population in 2020. Do you think the prediction will be too high or too low? Why?