Table 5 presents live‑birth rates specific for age of mother and urban/rural residence for as many years as possible between 1990 and 1998.
Description of variables: Age is defined as age at last birthday, that is, the difference between the date of birth and the date of the occurrence of the event, expressed in completed solar years. The age classification used in this table is the following: under 20 years, 5‑year age groups through 40‑44 years, and 45 years and over.
The urban/rural classification of births is that provided by each country or area; it is presumed to be based on the national census definitions of urban population.
computation: Live‑birth rates specific for age of mother are the annual number
of births in each age group per
Birth rates by age of mother and urban/rural residence are the annual number of live births that occurred in a specific age-urban/rural group (as shown in table 4) per 1 000 females in the corresponding age‑urban/rural group.
Since relatively few births occur to women below 15 or above 50 years of age, birth rates for women under 20 years of age and for those 45 years of age and over are computed on the female population aged 15‑19 and 45‑49, respectively. Similarly, the rate for women of "All ages" is based on all live births irrespective of age of mother, and is computed on the female population aged 15‑49 years. This rate for "All ages" is known as the general fertility rate.
Births to mothers of unknown age have been distributed proportionately on the basis of births to mothers of known age by the Statistics Division of the United Nations prior to computing the rates.
The population used in computing the rates is estimated or enumerated distributions of females by age. First priority was given to an estimate for the mid‑point of the same year. Second priority was given to census returns of the year to which the births referred, and third priority to an estimate for some other point of time in the year.
Rates presented in this table have been limited to those for countries or areas having at least a total of 100 live births in a given year. Moreover, rates specific for individual sub‑categories based on 30 or fewer births are identified by the symbol (").
Reliability of data: Rates computed using data from civil registers of live births which are reported as incomplete (less than 90 per cent completeness) or of unknown completeness are considered unreliable and are set in italics rather than in roman type. Table 1 and the technical notes for that table provide more detailed information on the completeness of live‑birth registration. 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: Rates shown in this table are subject to all the same limitations that affect the corresponding frequencies and are set forth in the technical notes for table 4.
These include differences in the completeness of registration, the treatment of infants who were born alive but died before the registration of the birth or within the first 24 hours of life, the method used to determine age of mother and the quality of the reported information relating to age of mother. In addition, some rates are based on births tabulated by date of registration and not by date of occurrence; these have been indicated by a (+).
The effect of including delayed registration on the distribution of births by age of mother may be noted in the age‑specific fertility rates for women at older ages. In some cases, high age‑specific rates for women aged 45 years and over may reflect age of mother at registration of birth and not fertility at these older ages.
The method of distributing the unknown ages is open to some criticism because of the fact that the age‑of‑mother distribution for legitimate births is known to differ from that for illegitimate births and that the proportion of births for which age of mother is unknown is higher among illegitimate births than it is among legitimate births.
The comparability of data by urban/rural residence is affected by the national definitions of urban and rural used in tabulating these data. It is assumed, in the absence of specific information to the contrary, that the definitions of urban and rural used in connection with the national population census were also used in the compilation of the vital statistics for each country or area. However, the possibility cannot be excluded that, for a given country or area, the same definitions of urban and rural are not used for both the vital statistics data and the population census data.
In addition to problems of comparability, vital rates classified by urban/rural residence are also subject to certain special types of bias. If, when computing vital rates, different definitions of urban are used in connection with the vital events and the population data and if this results in a net difference between the numerator and denominator of the rate in the population at risk, then the vital rates would be biased. Urban/rural differentials in vital rates may also be affected by whether the vital events have been tabulated in terms of place of occurrence or place of usual residence. This problem is discussed in more detail in section 18.104.22.168 of the Technical Notes.
Coverage: Live‑birth rates specific for age of mother are shown for 102 countries or areas. Rates are presented by urban/rural residence for 44 countries or areas.
Earlier data: Live‑birth rates specific for age of mother have been shown for the latest available year in each issue of the Yearbook. For information on specific years covered, readers should consult the Index.