Adult Population Projection under Generalized Population Model with Application to the Indian Census Age-returns

In classical population projection it is inherently assumed equality between census survival ratios and the corresponding life table survival ratios, which hold true only when the population under study is stationary or stable. The proposed technique makes use of ten-year cumulative census survival ratios which run more smoothly than the conventional census survival ratios (as shown by Coale and Demeney, 1967). These ten-year cumulative census survival ratios have been estimated from the corresponding ten-year cumulative life table survival ratios (defined by the ratio Tx+10/Tx in life table terminology) through a formula developed by Lahiri (2003) under generalized population model assuming that the age-specific growth curve follows a second-degree polynomial. The technique proposed here has been applied to project the Indian populations in 2001 and 2011 taking 1991 and 2001 census age-returns as bases respectively. The projected age-sex populations in 2001 and 2011 are sufficiently close to those of the 2001 enumerated population and 2011 expected population respectively. The technique can also be extended for long-term adult population projection by estimating the prospective growth rates over time.