A two step approach is taken in generating estimates of the under-five mortality rate (U5MR) and the infant mortality rate (IMR).

The first step is to obtain as much of the data from existing sources, to further process these data where necessary (such as in the case of data on children ever born and children surviving), and to plot all such data on a chart of U5MR or IMR against reference year of the data.

Unlike many indicators, the methodology used in deriving mortality data provides a historical time series from each survey source.

The second step is to fit a line to these data such that the line provides the best estimates of U5MR or IMR given the available data. Such a methodology has been developed and has been described and utilized for nearly a hundred countries in the report Trends in Child Mortality in the Developing World: 1960-1996, K. Hill et al, 1998, UNICEF. [This report can be found via Internet at http://www.childinfo.org]