The JMP estimates of national, regional and global access to drinking-water and sanitation are essentially based on data from national household surveys and censuses that are produced by the national statistics offices and other relevant government agencies. Establishing and maintaining a link with these agencies is essential for the JMP to ensure regular updates of its data.
The number of national household surveys and censuses available to the JMP has increased has increased six-fold from 272 to 1658 since 2000, as shown in the figure on the right. This has been dramatic over the past years due to direct contact with national agencies and collaboration with other data gathering mechanisms and networks (i.e. International Household Survey Network and its Accelerated Data Programme). The results of the data collection and updates varies from country to country but this networking approach has proven to be efficient and effective. Another important benefit of collaboration is the JMP's ability to directly resolve questions that arise during data analysis with the national monitoring agencies (see data reconciliation).
Currently the JMP database includes about 2000 national data-sets, majority of these are nationally representative household surveys and censuses (details can be found in the definitions and method section). Almost all of these come from developing regions and to a lesser extent from the MDG region of Caucasus and Central Asia (formerly known as Commonwealth of Independent States; Russian Federation, Ukraine and Belarus have been moved out of this group to MDG region of Developed countries to form this new MDG region). Since household surveys are practically nonexistent and censuses in many developed countries no longer collect information on water and sanitation, for these countries the JMP largely relies on administratively reported data. The JMP database currently includes more than 300 administratively reported data for developed countries.