The question of the gap between projected population and the actual 1971 census figures and the causes of the gap are discussed, and the impact of family planning is explored. The projection was based on the percentage decline of general fertility rate and the annual increase of life expectancy at birth. The census population for 1971 was 547 million against the projected figure of 563 million, a difference of 16 million. It is hypothesized that the difference is due to a great extent to the impact of the nationwide Family Planning Program. It is also hypothesized that in making the projections that either the general fertility rate and mortality were incorrect or that the migration factor was ignored. Extensive appendices are included that give the performance of the family planning program in India.