Middle fertility rates in the preferred series are assumed to hold at their initial 1990-1995 levels throughout the projection horizon. Initial rates are calculated from modified 1990 census counts and recorded area deaths by age and sex from the Missouri Department of Health for the period 1990-1995. Life expectancies have grown steadily over the last two decades. Recent Migration in the Preferred Series Migration assumptions are particularly critical because migration has generally changed area populations more than the birth and death components have changed them. The recent migration scenario is applied in the preferred projection series.
Migration is derived from net rates for males and females in each five-year age group in each area.
The rates are calculated in four stages. First, 1980-1990 net migration totals are computed as residuals using the vital statistics method. The 1990-1995 controls are used to project 1995 area populations by age and sex. In the fourth and final calculation stage, migration controls are constrained to avoid compounding net migration gains or losses in the several projection cycles to 2025. All migration controls and projected net migration for individual age-sex groups are rounded to the nearest whole number.