Life expectancy at birth

(a)           Name:  Life expectancy at birth.
(b)           Brief Definition:  The average number of years that a newborn
could expect to live, if he or she were to pass through life subject to the
age-specific death rates of a given period. 
(c)           Unit of Measurement:  Life expectancy at birth as expressed in
years.

(a)           Agenda 21:  Chapter 6: Protecting and Promoting Human Health.
(b)           Type of Indicator:  State. 

(a)           Purpose:  Measures how many years on average a new-born baby is
expected to live, given current age-specific mortality risks.  Life expectancy
at birth is an indicator of mortality conditions and, by proxy, of health
conditions.  It is also one of the most favoured indicators of social
development, and is used as one of the components of United Nations
Development Programme's (UNDP) Human Development Index.

(b)           Relevance to Sustainable/Unsustainable Development:  Mortality,
with fertility and migration, determines the size of human populations, their
composition by age, sex, and ethnicity, and their potential for future growth.

Life expectancy, a basic indicator, is closely connected with health
conditions, which are in turn an integral part of development.  The ICPD
Programme of Action notes that the unprecedented increase in human longevity
reflects gains in public health and in access to primary health-care services
(paragraphs 8.1 and 8.2), which Agenda 21 recognizes as an integral part of
sustainable development and primary environmental care (paragraph 6.1).  The
ICPD Programme of Action highlights the need to reduce disparities in
mortality and morbidity among countries and between socioeconomic and ethnic
groups. It identifies the health effects of environmental degradation and
exposure to hazardous substances in the work-place as an issue of increasing
concern.

(c)           Linkages to Other Indicators:  This indicator reflects many
social, economic, and environmental influences.  It is closely related to
other demographic variables, particularly the population growth rate.  It also
has linkages with indicators of human health and the environment as well as
economic indicators. Examples of closely linked indicators would include
infant mortality, and water and air quality.  

(d)           Targets:   The Declaration of Alma Ata (1978) set a target of
life expectancy greater than 60 years by the year 2000, and the ICPD Programme
of Action revised the target: life expectancy should be greater than 65 years
by 2005 and 70 years by 2015 for countries that currently have the highest
levels of mortality; and 70 years and 75 years, respectively, for the other
countries (ICPD Programme of Action, paragraph 8.5).

(e)            International Conventions and Agreements:  See section 3d
above.

Calculation of life expectancy at birth is based on age-specific death rates,
which may be calculated separately for males and females, or for both sexes
combined.  The death rates are commonly tabulated for ages 0 to 1 years, 1 to
5 years, and for 5-year age groups for ages 5 and above.  Where data on deaths
by age are of good quality, or adjustments for age mis-statement and
incompleteness can be made, the life expectancy at birth can be calculated
directly from registered deaths and population counts, which are usually based
on census enumerations, evaluated and, if necessary, adjusted.  Several steps
are needed to derive life expectancy from age-specific death rates; the
details can be found in demographic or actuarial references that describe
construction of life tables, for example, Pressat (1972) or Shryock and Siegel
(1980).  For a description of the methodology that is linked to computer
routines to aid in the calculation, see MORTPAK-LITE (item 7, below).

When data on deaths by age are unavailable from registration systems or sample
surveys, the life expectancy at birth can be calculated through "indirect"
methods based on special questions asked in censuses or demographic surveys. 
For information on these indirect estimates, see Manual X and MORTPAK-LITE
(section 7, below).

Data is collected by the United Nations on a regular basis and available for
most countries from vital registration systems or surveys.  For all countries,
census and registration data are evaluated and, if necessary, adjusted for
incompleteness by the Population Division, United Nations Department of
Economics and Social Information and Policy Analysis (DESIPA) as part of its
preparations of the official United Nations population estimates and
projections.  Past, current and projected estimates of life expectancy at
birth are prepared for all countries by the Population Division, DESIPA and
appear in the United Nations publication, World Population Prospects: The 1994
Revision (see section 7, below).

Most countries tabulate data from death registration systems at the sub-
national level.  The infant mortality rate and the crude death rate (annual
number of deaths per thousand population) is more readily available for sub-
national units than is life expectancy at birth.

The lead organization is the United Nations DESIPA.  The contact point is the
Director, Population Division, DESIPA; fax no. (1 212) 963 2147.  At the World
Health Organization, the contact person is the Director, Office of Global and
Integrated Environmental Health; fax no. (41 22) 791 4123.

DESIPA. World Population Prospects: The 1994 Revision. Population Division.
United Nations Sales No. E.95.XIII.16, New York, 1995. 

DESIPA. Manual X: Indirect Techniques for Demographic Estimation. Population
Division United Nations Sales No. E.83.XIII.2, New York, 1983.

DESIPA. MORTPAK-LITE - The United Nations Software Package for Mortality
Measurement.  Population Division.  United Nations,  New York, 1988.

DESIPA. Demographic Yearbook. Statistical Division. United Nations Sales      
No.E/F.95.XIII.1,1995.  1993.

Pressat, R.  Demographic Analysis: Methods, Results, Applications.  London,
Edward Arnold; Chicago, Aldine Atherton.  1972.

United Nations.  Report of the International Conference on Population and
Development. Programme of Action of the International Conference on Population
and Development.  United Nations Document A/CONF. 171/13.  Cairo, Egypt,
September 5-13, 1994.  

Shryock,  H.S, and J.S.Siegel.  The Methods and Materials of Demography.  U.S.
Government Printing Office,  Washington, D.C.  1980.

LEAD AGENCY: DESIPA