They have made available online some very important datasets relating to a number of health indicators, which have much wider coverage than most other sources.
For example, a recent paper in the Lancet documents the progress made in reducing global maternal mortality in childbirth. The authors have compiled a database for 181 countries from 1980 to 2008, using available information from a wide variety of sources including surveys and vital statistics. They estimate there were a total of 342,900 such deaths in 2008, compared to 526,300 in 1980. Despite some progress, 80% of all deaths are concentrated in 21 countries. The bottom five comprises India, Nigeria, Pakistan, Afghanistan, and Ethiopia. An interesting case is Egypt which has seen an annual decrease of 8.4% between 1998 and 2008. In comparison to other developed nations, the US has performed poorly during this period.
Another paper, also published in the Lancet examines trends in the financing of public health expenditure in developing countries, and finds that there are important crowding out effects of development assistance for health.
The same team has done similarly valuable work building a global database for child mortality.