ASi" kUCTURE FlOR DEVELOPMENT

E000
*t Technical notes'
The main critenon for country classification is gross Base yers
national product (GNP) per capita. Vith the addition
of the recently independent republics of the for- To provide long-term trend analysis, facilitate intermer
Soviet Union, the main tables now include national comparisons, and include the effects of
country data for 132 economies, listed in ascending changes in intersectoral relative prices, constant
GNP per capita order A separate table (Table la) price data for most economies are partially rebased
shows basic indicators for 75 more economies with to tiree base years and linked together- The year
sparse data or with populations of fewver than 1 nil- 1970 is the base year for data from 1960 to 1975,1980
lion. Other changes are outlined in the Inhtroduction. for 1976 to 1982 and 1987 for 1983 and beyond.
These three periods are "chain-linked" to obtain
Data refiabil7ity
1987 prices throughout all three periods.
Chain-linking is accomplished for each of the
Considerable effort has been made to standardize three subperiods by rescaling; this moves the year in
the data, but full comparability cannot be ensured, which current and constant price versions of the
and care must be talen in interpreting the indica- same time series have the same value, without altertors
Mlany factors affect availability and reliability; ing the trend of either. Components of gross domesstatistical
systems in many developing economies tic product (GDP) are individually rescaled and
are still -weak, statistical methods, coverage, prac- summed to provide GDP and its subaggregates- In
tices, and definitions differ widely among countries; this process a resaling deviation may occur beand
cross-country and cross-time comparisons in- tween the constant price GDP by industrial origin
volve complex technical problems that cannot be and the constant price GDP by expediture Such
unequivocally resolved. For these reasons, although rescling deviations are absorbed under the heading
the data are drawn from the sources thought to be privte consmption, etaC on the assumption that GDP
most authoritative, they should be construed only by industrial ongin is a more reliable estimate than
as indicating trends and characterizing major differ- GDP by expenditure
ences among economies rather than offering precise Becaute private consumption is calculated as a
quantitative measures of those differences. In partic- residual, the national accounting identities are
ular, data issues have yet to be resolved for the fif- maintained. Rebasing does involve incorporating in
teen economies of the former Soviet Union. Cover- private consumption whateverstatistical dscrepanage
is sparse, and the data are subject to more than des arise for expenditure The value added in the
the normal range of uncertainty-
services sector also includes a statistical discrep-
Most social and demographic data from national ancy, as reported by the original source.
sources are drawn from regular administrative files,
although some come from special surveys or peri- Summary measures
odic census inquiries. In the case of survey and census
data, figures for intermediate years have to be The summary measures are calculated by simple
interpolated or otherwise estimated from the base addition when a variable is expressed in reasonably
reference statistics. Similarly, because not all data comparable units of account Economic indicators
are updated, some figures-especialy those relat- that do not seem naturally additive are usually coming
to current periods-may be extrapolated. Sev- bined by a price-weighting scheme The summary
eral estimates (for example, life expectancy) are de- measures for social indicators are weighted by poprived
from models based on assumptions about ulation.
recent trends and prevailing conditions. Ii;sues re- The World Development Indicators, unlike the
lated to the reliability of demographic indicators are World Tables, provide data for, usually, two reference
reviewed in United Nations, World Popuathon Treds points rather than annual time series. For summary
and Policies. Readers are urged to take these linita- measures that cover many years, the calculation is
tions into account in interpreting the indicators, based on the same countrv composition over time
particularly when making comparisons across and across topics. The World Development Indicaeconomies.
tors pernit group measures to be compiled only if
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