PIP: In this article, the concept--population investment--relates to population and economy for investment expenditures and economic gains. 3 economic approaches express this concept. 1) Population investment, which maintains the standard of living, may be considered separate from economic investment, which raises the per capita income. The original population and the increased population comprise total population. Increased population, composed of newborns, is nonproductive, lowering per capita output. Rapid population growth increases population investment and decreases economic investment so that the national economy does not improve. 2) Population investment regards people as producers in a narrow as well as broad sense. Each potential worker incurs labor reproduction expenses since he must be reared and educated before he becomes a producing laborer. Family and society labor reproduction expenditures depend upon costs for 1) prenatal care and delivery, 2) living expenses, 3) medical fees, 4) educational fees, and 5) related state expenditures, such as maternity wages and infant mortality costs. A 1979 study, using 191 cities, estimated costs of 6907 yuan in cities, 4830 yuan in towns, and 1630 yuan in rural areas to raise a child from conception through age 16. Researchers conclude that 1) raising the new labor force is more expensive in towns and cities than in rural areas, 2) families supply over 70% and the state less than 30%, of costs, and 3) living expenses make up over 60% of costs, with education taking 11.3% (rural) to 26.8% (urban). 3) Education fees (intelligence investment) form the third population investment function. Changes in labor quality as they effect national income illustrate the effects of intelligence investment. The authors theorize that intelligence investment is a fourth factor, with 1) increased work force size, 2) increased gross output, and 3) reduced material consumption in increasing the national income.