life table models การใช้

• Similarly, in pre-modern societies for which evidence is available, such as early modern England and early eighteenth-century China, infant mortality varies independently of adult mortality, to the extent that equal life expectancies at age twenty can be obtained in societies with infant mortality rates of 15 % to 35 % ( life table models omit this; they depend on the assumption that age-specific mortality ratios co-vary in uniform, predictable ratios ).