**Table
3**

Table 3
presents selected derived measures of natality for as many years as possible
between 1980 and 1999. These
measures are the child-woman ratio, the total fertility rate and the gross and
net reproduction rates.

Description of
variables: The child-woman ratio is the number of children under five-years of
age per

The
child-woman ratio may be thought of as an indicator of recent fertility net of
child mortality. The child-woman
ratio is, in effect, the number of surviving births from the five years prior to
the reference date, often the time of a population census, per

The total
fertility rate is the average number of children that would be born alive to
hypothetical cohort of women if, throughout their reproductive years, the
age-specific fertility rates for the specified year remain unchanged. The total fertility rate is the sum of
the age-specific fertility rates per woman. The structure of the population does not
affect the total fertility rate because each age group is weighted
equally.

The gross
reproduction rate is the average number of daughters that would be born alive to
a hypothetical cohort of women if they lived to the end of their reproductive
years and if they experienced the some age-specific fertility throughout their
lives that women in each age group experience in a given year or period of
years. Although the gross
reproduction rate purports to describe the fertility experience of a generation
of women, the rates presented in this table are actually based on the fertility
reported or estimated for a given reference period, usually a single year or a
five-year period.

The gross
reproduction rate is not affected by the age structure of the population because
it is, in effect, an age-standardized fertility rate with each age given a
weight of one. In addition, it can
also be thought of as the ratio between female births in two successive
generations assuming that there are no deaths before the end of the reproductive
period, or it may be considered as the ratio between the number of females in
one generation at a given age and the number of their daughters at the same age,
assuming that there is no mortality during the child-bearing
years.

In a
female population unaffected by mortality and migration, and assuming the
age-specific fertility rates of the reference period do not change, a gross
reproduction rate of one indicates exact replacement, a rate of less than one
indicates that the population is not replacing itself while a rate of more than
one means that the population is more than replacing itself. Because of the
impact of mortality, gross reproduction rates somewhat in excess of one are
needed to achieve replacement.

The net
reproduction rate is the average number of daughters that would be born alive to
a hypothetical cohort of women if they experienced the same age-specific
fertility throughout their lives that women in each age group experienced in a
given year, or period of years, and if they were also subjected to the mortality
rates of the same year or period of years.
Although the net reproduction rate purports to describe the fertility and
mortality experience of a generation of women, the rates presented in this table
are actually based on the fertility and mortality reported or estimated for a
given reference period, usually a single year or a five-year
period.

Like the
gross reproduction rate, the net reproduction rate is not affected by the age
structure of the population.
However, it differs from the gross reproduction rate because it takes
mortality into account.

The net
reproduction rate can also be thought of as the ratio between female births in
two successive generations taking mortality into account, or it may be
considered as the ratio between the number of females in one generation at a
given age and the number of their daughters at the same age, again taking
mortality into account.

In a
female population unaffected my migration and assuming the age-specific
fertility and mortality rates of the reference period do not change, a net
reproduction rate of one indicates exact replacement, a rate of less than one
indicates that the population is not replacing itself while a rate of more than
one means that the population is more than replacing itself. A net reproduction rate of one is
roughly equivalent to a two-child family.

Ratio and rate
computation: Child-woman ratios are the number of children of both sexes 0-4
years of age per

The
child-woman ratios have been computed by the Statistics Division of the United
Nations unless otherwise noted.
When the basic official data with which to compute these ratios have not
been available, estimates prepared by the Population Division of the United
Nations Secretariat[1] have been included; these are indicated
by footnotes.

Child-woman
ratios presented in this table have not been limited to those countries or areas
having a minimum number of children under 5 years of age. However, ratios shown in this table
based on 30 or fewer children under 5 years of age are identified by the
symbol(♦).

Total
fertility rates are the sum of age-specific fertility rates. The standard method of computing the
total fertility rate is to sum the age-specific fertility rates. However, if the rates used are fertility
rates for 5-year age groups, they must be multiplied by 5. The total fertility rates have been
computed by the Statistics Division of the United Nations unless otherwise
noted. When the basic official data
with which to compute these rates have not been available, estimates prepared by
the Population Division of the United Nations Secretariat[1] have been included; these are indicated
by footnotes.

Total
fertility rates presented in this table have not been limited to those countries
or areas having a minimum number of live births in a given year. However, rates based on 30 or fewer live
births shown in this table are identified by the
symbol(♦).

The gross
and net reproduction rates were computed by national statistical
offices.

The
standard method of computing the gross reproduction rate is to sum the
age-specific fertility rates for female live births. If the rates used are for other than
single years of age, for example, if they are for 5-year age groups, they must
be multiplied by 5. The sum of
these rates is the gross reproduction rate.

An
alternative method of computing the gross reproduction rate is to multiply the
total fertility rate by a factor (0.484 or 0.488 are commonly used), which
approximates the proportion of female to total births.

The net
reproduction rate is computed the same way as the gross reproduction rate, but
with additional steps to take mortality into account. Before summing, the individual
age-specific fertility rates are multiplied by the proportion of females
surviving from birth to the midpoint of the corresponding age interval. These proportions can be computed using
the following functions from a life table for females: (Lx/lo), lo being the
radix of the table. The life table
should be for the same year or period of years to which the age-specific
fertility rates pertain.

An
alternative method of computing the net reproduction rate is to take the gross
reproduction rate and then simply multiply it by the probability of female
surviving from birth to the mean age of maternity, computed in the absence of
mortality.

The gross
and net reproduction rates shown in this table are based on female fertility and
female fertility and mortality, respectively. It is also possible, but by no means the
standard practice, to compute analogous rates for the male population. In
addition, as presented here, these rates refer to a hypothetical cohort based on
fertility schedules for a given year or period of years. These rates can also be
computed for a real cohort, representing their fertility (and
mortality).

Gross and
net reproduction rate presented in this table have not been limited to those
countries or areas having a minimum number of live births in a given
year.

Reliability of
data: Child-woman ratios computed using estimates which are believed to be less
reliable are set in italics rather than in roman type. Classification in terms of reliability
is based on the method of construction of the total population estimate as shown
in the regular Demographic Yearbook in the volume containing the general tables
and discussed in the technical notes for the table. No attempt has been made to
take account of age-reporting accuracy.

Total
fertility rates computed using data from civil registers of live births that are
reported as incomplete (less than 90 per cent completeness) or of unknown
completeness are considered unreliable and are replaced by estimates prepared by
the Population Division of the United Nations Secretariat[1]. For more information about the quality
of vital statistics data in general, and the information available on the basis
of the completeness estimates in particular, see section 4.2 of the Technical
Notes.

Limitations:
Child-woman ratios shown in this table are subject to all of the same
limitations that affect the data on population by age and sex from which they
have been computed. Although the
interpretation of child-woman ratios is usually based on the presumption that
differences between countries or areas reflect differences in the rates at which
births occurred to women of child-bearing age in the five years preceding the
census, these ratios are strongly influenced by other factors, the most
important of which are deficiencies and irregularities in the census
results.

Although
under enumeration at the census may occur in any age group and hence may affect
both the numerator and the denominator of the ratio, it appears that in most
censuses, a greater proportion of young children is omitted from the count than
of older persons. The number of
young children recorded in the census is also affected by the tendency to give
rounded statements of age, with the result that some children under 5 may be
mistakenly included among those who are 5 or over. Moreover, in countries or areas where
the Chinese method of counting age is traditional, census returns will reflect
the fact that infants are considered to be one year of age at birth and gain one
additional year at the Chinese New Year. Adjustments can be made in these data
to bring them approximately into accord with results of the Western-type
question, but failing this, the child-woman ratios will tend to be
understated.

The
ratios shown in the table are, therefore, without doubt somewhat lower than they
would be if census data on age were fully accurate. On the other hand, in
countries or areas where people generally do not know their ages, it is possible
that the ratios may be too high. On the whole, they are probably less deficient
in the countries or areas where they are low, since many of these have good
statistics. In any case, regarding countries or areas with poor census data on
age (and many of the countries or areas with high ratios fall into this
category), even fairly large differences in the ratios may be due mainly or
entirely to deficiencies in the data.

Unlike
other derived measures of fertility shown in this table, it should be remembered
that the child-woman ratio is an indicator of recent fertility net of child
mortality. Therefore, another
factor affecting the utility of the ratios as fertility measures, is
mortality. Even if the data were
completely accurate, the ratios would not necessarily correspond closely to the
rate at which births have occurred to women of child-bearing age in the years
just before the census. The number
of children under five living at a given time is the number who have survived
among children born during the preceding five years. The ratios, therefore, invariably
understate actual fertility levels.
Furthermore, death rates at these ages vary widely from one part of the
world to another. Countries or
areas with high fertility tend also to be those with high child mortality.

Consequently,
the ratios for such places are more affected than those places with low
fertility and mortality, and the gap between those with high and those with low
ratios is narrower than the gap between them in the frequency of births. However, ratios of children to women of
child-bearing age are more useful for some types of analysis than rates based on
births and population. If one
wishes to study the rate at which the older generation is likely to be replaced
by its offspring, children who die in infancy are irrelevant. From this point of view, differences in
infant mortality do not affect the comparability of the ratios
shown.

Although
the child-woman ratio is much less affected than the crude birth rate by the age
and sex structure of the population, variations in the age structure of the
female population in the reproductive years can affect the international
comparability of these ratios.

Total
fertility rates shown in this table are subject to all the same limitations that
affect the data on live births by age of mother and the data on population by
age and sex from which they have been computed.

Gross and
net reproduction rates shown in this table are subject to all the same
limitations which affect data on live birth rates specific for age of mother
and, in addition, for the net reproduction rates.

In this
connection, it should be borne in mind that the female age-specific fertility
and mortality rates recorded in a given country or area at a given time do not
actually represent the experience of any real generation of women, and that they
may be influenced by factors which are by their nature, necessarily
temporary. They are useful as a
means of demonstrating the implications of fertility (and mortality) schedules
pertaining to a given year or period of years assuming they were to continue
unchanged.

Moreover,
these rates do not take account of the fertility and mortality of the male
population. There are important
considerations in using gross and net reproduction rates as means of analysing
the implications of observed fertility and mortality rates for future population
development.

In the
absence of information to the contrary, it is assumed that rates in this table
were computed by the methods described above under “Ratio and rate
computation”. However, gross
reproduction rates for the same countries or areas derived from the age-specific
fertility rates given in table 5 may not be exactly the same as those found in
this table. This is because the
latter may have been computed on different estimates of the female population or
they may have involved special adjustments for under-registration of birth or
for treatment of births for which the age of mother was
unknown.

The
accuracy of net reproduction rates is affected also by the accuracy of the life
tables used. Some special questions
arise in net reproduction rate computation in regard to the period of time to
which the life tables relate. The
life table used here is frequently the one computed from the death rates of
women in the year to which the fertility rates relate, but often life tables for
other years are used; in those cases, the value of a net reproduction rate is
likely to fluctuate far more as a result.
This procedure has been followed in this table.

Coverage:
Selected derived measures of natality are shown for **224** countries or
areas.

Earlier data:
Selected derived measures of natality have been shown in the Demographic
Yearbook: Historical Supplement and 1975, 1981 and 1986 issues. Each of the measures included in this
table may also be found in earlier issues of the Demographic Yearbook as
indicated in the Index.

** **

[1] *World Population
Prospects, Comprehensive Tables*, Sales No.
E. 01.XIII.8 & CORR.1, United Nations, New York,
2000.