c - usaid

where C m
iG the index of marriage, C is the index of
0
induced abortion, C is the index of postpartum
infecundabi L Ity, and a Ll terms containing (o) refer to the
b s year whosu values can be asrumed to be known. That
leaver three terms re fe rri ng to the target year, namely C m
C end C Of these, C. cnin be assumed to be age-i nvari ant,
a i i
but C end C very with age. Therefore, anothor
m
a
rat i o
namely
ASFII t,e )
1- 6 a I).U[ t ,a)I . ( t , )I .C [(t, a)I. C [(t ,o)
S
a
is pre fereb Le to rat io (3.5] from the viewpoint of
identifying a re lat ive ly more stab le input that can take the
place of ASFR (t) . This ratio can be a ssumed to take the
value
ASFR(O, ) C (t)
---------------------------------------
C(o,a]).0
------
fO,o) .C (o,a]
C to]
c m a i
which iG a slowly inc rcasIng function of t as already
mentioned in cection 2.
VIe can cat l the ratio (3.7) as the age-specific
natural ferti Li ty
rate.