The 21st Century climate challenge

expectancy estimates published by UNPD areusually five-year averages although it does alsoproduce annual life expectancy estimates interpolatedfrom the five-year averages. The lifeexpectancy estimates for 2005 shown in Table1 and those underlying Table 2 are from theseinterpolated data. For details on World PopulationProspects 1950–2050: The 2006 Revisionsee www.un.org/esa/population/unpop.htm.Adult literacy rate. This Report uses dataon adult literacy rates from the United NationsEducational, Scientific and Cultural Organization(UNESCO) Institute for Statistics(UIS) April 2007 Assessment (UNESCO Institutefor Statistics 2007a), that combines directnational estimates with recent estimatesbased on its Global age-specific literacy projectionsmodel developed in 2007. The nationalestimates, made available through targeted effortsby UIS to collect recent literacy data fromcountries, are obtained from national censusesor surveys between 1995 and 2005. Where recentestimates are not available, older UIS estimates,produced in July 2002 and based mainlyon national data collected before 1995, havebeen used instead.Many high-income countries, having attainedhigh levels of literacy, no longer collectbasic literacy statistics and thus are not includedin the UIS data. In calculating the HDI,a literacy rate of 99.0% is assumed for high-incomecountries that do not report adult literacyinformation.In collecting literacy data, many countriesestimate the number of literate people basedon self-reported data. Some use educational attainmentdata as a proxy, but measures of schoolattendance or grade completion may differ. Becausedefinitions and data collection methodsvary across countries, literacy estimates shouldbe used with caution.The UIS, in collaboration with partneragencies, is actively pursuing an alternativemethodology for measuring literacy, the LiteracyAssessment and Monitoring Programme(LAMP). LAMP seeks to go beyond the currentsimple categories of literate and illiterateby providing information on a continuum ofliteracy skills. It is hoped that literacy ratesfrom LAMP will eventually provide more reliableestimates.Combined gross enrolment ratios in primary,secondary and tertiary education. Grossenrolment ratios are produced by the UIS(UNESCO Institute for Statistics 2007c) basedon enrolment data collected from national governments(usually from administrative sources)and population data from the World PopulationProspects 1950–2040: The 2004 Revision. Theratios are calculated by dividing the numberof students enrolled in primary, secondary andtertiary levels of education by the total populationin the theoretical age group correspondingto these levels. The theoretical age group fortertiary education is assumed to be the five-yearage group immediately following on the end ofupper secondary school in all countries.Although intended as a proxy for educationalattainment, combined gross enrolmentratios do not reflect the quality of educationaloutcomes. Even when used to capture access toeducational opportunities, combined gross enrolmentratios can hide important differencesamong countries because of differences in theage range corresponding to a level of educationand in the duration of education programmes.Grade repetition and dropout rates can also distortthe data. Measures such as the mean yearsof schooling of a population or school life expectancycould more adequately capture educationalattainment and should ideally supplantthe gross enrolment ratio in the HDI. However,such data are not yet regularly available for asufficient number of countries.As currently defined, the combined grossenrolment ratio measures enrolment in thecountry of study and therefore excludes studentsstudying abroad from the enrolment ratioof their home country. Current data for manysmaller countries, for which pursuit of a tertiaryeducation abroad is common, could substantiallyunder estimate access to education oreducational attainment of the population andthus lead to a lower HDI value.GDP per capita (PPP US$). In comparingstandards of living across countries, economicstatistics must be converted into purchasingpower parity (PPP) terms to eliminate differ-226 HUMAN DEVELOPMENT REPORT 2007/2008