Table 1 presents live births by sex and live-birth rates by urban/rural residence for as many years as possible between1980 and 1999.
Description of variables: Live birth is defined as the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of pregnancy, which after such separation, breathes or shows any other evidence of life such as beating of the heart, pulsation of the umbilical cord, or definite movements of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached; each product of such a birth is considered live-born regardless of gestational age.
Statistics on the number of live births are obtained from civil registers unless otherwise noted.
The urban/rural classification of birth is that provided by each country or area; it is presumed to be based on the national census definitions of urban population.
Reliability of data: Each country or area has been asked to indicate the estimated completeness of the live births recorded in its civil register. These national assessments are indicated by the quality codes (C), (U), and (...) that appear in the first column of this table.
C indicates that the data are estimated to be virtually complete, that is, representing at least 90 per cent of the live births occurring each year, while U indicates that data are estimated to be incomplete, that is, representing less than 90 per cent of the live births occurring each year. The code (...) indicates that no information was provided regarding completeness.
Data from civil registers which are reported as incomplete or of unknown completeness (coded U or ...) are considered unreliable. They appear in italics in this table.
These quality codes apply only to data from civil registers. If a series of data for a country or area contains both data from a civil register and estimated data from, for example, a sample survey, then the code applies only to the registered data. If only estimated data are presented, the symbol (..) is shown instead of the quality code. 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: Statistics on live births are subject to the same qualifications as have been set forth for vital statistics in general and birth statistics in particular as discussed in section 4 of the Technical Notes.
The reliability of data, an indication of which is described above, is an important factor in considering the limitations. In addition, some live birth are tabulated by date of registration and not by date of occurrence; these have been indicated by a (+). Whenever the lag between the date of occurrence and date of registration is prolonged and, therefore, a large proportion of the live-birth registrations are delayed, birth statistics for any given year may be seriously affected.
Another factor which limits international comparability is the practice of some countries or areas not to include in live-birth statistics infants who were born alive but died before the registration of the birth or within the first 24 hours of life, thus underestimating the total number of life births. Statistics of this type are footnoted.
In addition, the sex distribution of births may be especially affected by the degree of incompleteness of birth registration. This is so because in some cultures it appears that female births tend to be less completely registered than male births, especially if the infant dies shortly after birth and before registration.
The comparability of data by urban/rural residence is affected by the national definition 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. The definitions of urban vary considerably from one area or country to another.
Coverage: Live births are shown for 191 countries or areas. Data are presented by urban/rural residence for 93 countries or areas.
Earlier data: Live births have been shown in each issue of the Demographic Yearbook. For information on specific years covered, readers should consult the Index.
 Principles and Recommendations for a Vital Statistics System Revision 2, Para.57, Sales No. E.01.XVII10, United Nations, 2001