completeness of vital- and population registration systems in the EC member countries, very reliable estimates.

Mortality estimates for other developed countries that are not EC members are often from an annual article wLa conjoncture demographique: LEurope et les pays developpds d'outre-mer* by Alain Monnier in the French journal _Population,_ published by the French Institut National d'gtudes Ddmographiques. These are also mostly recent and reliable registration based estimates and include IMR and life expectancy estimates.

_Tabki_ i. _Frequency of use of sources qf mortlty data_

|Source|.l|**Life**<br>exoectancy|
|---|---|---|
|**U.N. Population**<br>**Division**|**79**|**84**|
|**U.N. Statistical**<br>office|**47**|**39**|
|**Survey or census**<br>|**33**<br>|**24**<br>|
|**U.S.Bureauof**<br>**the Census**<br>**Other**|**13**<br>**26**|**8**<br> <br>**39**|

Surveyrepo,such as those produced _Notes: "Odter" coninsts of Eurostat, Monnier Official_ Survey reports, such as those produced _publications; and Bank aseme Totl does not add_ by the _Demographic and Health Surveys_ (DHS), as _to total_ **_number_** _of_ **_countries,_** _bt ause multiple sources are_ well as census publications are a frequent source of _used_ **_in_** _some cases._ IMR estimates. When surveys or census results have only recently become available, they are often not yet incorporated in U.N. or other sources. DHS data are generally considered to be of high qualitv and are particularly useful because they cover .iany countries which do not otherwise have adequate demographic statistics. DHS reports present IMR and under-five mortality (q5) estimates, from which life expectancy at birth is derived with a model life table.

Mortality estimates for some smnall countries, mostly in the Pacific and the Caribbean, are from a publication of the Center for International Research at the U.S. Bureau of the Census, _World Population Profitle: 1989._ The original sources of the estimates in this publication are not known, and while rates are internally consistent, they may lack a recent empirical basis.

For a fevw countries, estimates are obtained directly from publications issued by country statistical offices. These estimates may be based on vital registration or censuses or surveys and are used when they are mrre recent than those in previously listed sources.

# _Constrwting quinquenni&._ **_-4ut_** _single-year mortality rates_

Mortality estimates constructed by the Population and Human Resources Department of the World Bank are of two kinds: single-year estimates (i.e, 1989 IMR and life expectancy at birth estimates used in _World Development Report 1991)_ and quinquennial estimates (i.e, average rates for the period 1985-89). Trhe choice of procedures used in constructing either type depends largely on the availability of data.

Single-year IMR estimates for countries with complete vital registration systems are generally available from one of the sources listed above (except _World Population Prospects 1990,_ which gives only quinquennial figures). About one-third of all countries for which the Bank makes separate estimatec were classified by the U.N. Statistical Office as having complete vital registration (United Nations, various years). Five-year IMR estimates for the 1985-89 base quinquennium are usually the mean of single-year rates. Life expectancy at birth estimates tend to lag IMR and CDR estimates because life expectancy is a statistical abstraction that needs to be constructed from period 3