Methodology

Definition of indicators

Under-five mortality rate: Probability of dying between birth and exactly five years of age, expressed per 1,000 live births.

Infant mortality rate: Probability of dying between birth and exactly one year of age, expressed per 1,000 live births.

Neonatal mortality rate: Probability of dying during the first month of life, expressed per 1,000 live births.

Data sources and methods

The UN Inter-agency Group for Child Mortality Estimation (IGME) was formed in 2004 to share data on child mortality, harmonize estimates within the UN system, improve methods for child mortality estimation, report on progress towards the Millennium Development Goals and enhance country capacity to produce timely and properly assessed estimates of child mortality. The IGME, led by the United Nations Children’s Fund (UNICEF) and the World Health Organization (WHO), also includes the World Bank and the United Nations Population Division of the Department of Economic and Social Affairs as full members.

The IGME’s independent Technical Advisory Group, comprising leading academic scholars and independent experts in demography and biostatistics, provides guidance on estimation methods, technical issues and strategies for data analysis and data quality assessment.

Generating accurate estimates of child mortality poses a considerable challenge because of the limited availability of high-quality data for many developing countries. Complete vital registration systems are the preferred source of data on child mortality because they collect information as events occur and they cover the entire population. However, many developing countries lack fully functioning vital registration systems that accurately record all births and deaths. Therefore, household surveys, such as the UNICEF-supported Multiple Indicator Cluster Surveys and the US Agency for International Development–supported Demographic and Health Surveys, are the primary sources of data on child mortality in developing countries.

The IGME updates its child mortality estimates annually after reviewing newly available data and assessing data quality. The IGME seeks to compile all available national-level data on child mortality, including data from vital registration systems, population censuses, household surveys and sample registration systems. In preparing this round of estimates, a substantial amount of newly available data has been incorporated: data from the most recent surveys and censuses for about 30 countries, new data from vital registration systems for more than 50 countries and data from more than 70 surveys and censuses conducted before 2000 for about 20 countries. The increased data availability has resulted in substantial changes in the estimates for some countries from previous years.

Data from different sources require different calculation methods and may suffer from different errors, for example random errors in sample surveys or systematic errors due to misreporting. As a result, different surveys often yield widely different estimates of under-five mortality rate for a given time period. In order to reconcile these differences, the Technical Advisory Group of the IGME has developed methods to fit a smoothed trend curve to a set of observations and to extrapolate that trend to a defined time point, in this case 2010. To estimate the under-five mortality trend series for each country, a statistical model is fitted to data points that meet quality standards established by the IGME and then used to predict a trend line that is extrapolated to a common reference year, set at 2010 for the estimates in this report. To predict infant mortality rates, model life tables are used to transform under-five mortality rates. To predict neonatal mortality rates, a statistical model is used to transform under-five mortality rates.

Because the fitted under-five mortality rate trend line is based on the entire time series of data available for each country, this round of estimates may differ from and not be comparable with previous sets of IGME estimates and the most recent underlying country data.

More details on the data used in the deriving estimates are available in the IGME’s child mortality database, CME Info (www.childmortality.org). Details of methodology will be forthcoming in a peer-reviewed article and will be available upon request.

Comments and limitations (data quality)

In the majority of developing countries, under-five mortality rate estimates are obtained from household surveys and therefore have attached confidence intervals that need to be considered when comparing values along time or across countries. Similarly, these estimates are often affected by non-sampling errors that may affect equally recent levels and trends of under-five mortality rate. Click on the links to access An Assessment of the Credibility of Child Mortality Declines Estimated from DHS Mortality Rates and Comparison of spline- and loess-based approaches for the estimation of child mortality.

Key references