While national statistics are helpful to national planners and international agencies, a more local picture is also needed.  This picture cannot be built up from simple coverage statistics, because it would require that all countries use indicators that meet the specific monitoring requirements used by the Joint Monitoring Programme.

Household surveys have been used extensively to improve the quality of data and to get a better picture of coverage.  Nevertheless, there are still important problems with the comparability of data (definitions aren't always the same, surveys do not uniformly cover all regions within a country, etc.).

Data collection and processing techniques are improving, and each year provide a clearer picture of conditions in different parts of the world.  In turn, this helps policy-makers and others set priorities for concerted actions.