One problem every developing country shares is a lack of information about their population. How many people live in the country, where are they, what do they do for a living, where do they go to school, how healthy are they?
In rich countries this information is largely collected by service providers and automated systems – your employer knows your national insurance number and reports your earnings to the taxman; your doctor records that you visited and what was discussed. Your children are enrolled in a school and their exam results are compiled with all other children and available nationally. We know who has water through the records of water companies.
The systems to collect, store and use this information are expensive – they require hardware (ICT), skilled professionals, and large amounts of manpower inputting and administrating the information, and they only work for national data because very nearly everybody has access to, and uses, the state apparatus.
In lieu of this wealth of information, poorer countries take a more direct approach – the household survey. These involve a team of trained people going to randomly selected households and asking the people who live there a long series of questions about their lives.
These are blunter instruments than the above data – they can rarely be disaggregated beyond quite large areas, and they are time consuming, so can only cover the really essential items. They also may undercount the urban poor, either because the questioners avoid spending time in slums or because some of the people do not have ‘households’ that can be identified because they sleep on the street or at work. But they do produce nationally representative results and give a lot of useful information.
One of the most important advantages to this method is that they count people who are not using official services, and they tell us what those people actually do instead. In Africa, the WHO/Unicef JMP estimates that only 16 percent of people have piped water into their homes; if we only looked at data from piped water suppliers, as is the norm in the UK or USA, we would only have information on a sixth of the population, probably nearly all the most wealthy urban dwellers.
Many surveys, such as DHS and MICS, are funded by donors (USAID and UNICEF respectively) and are publicly available. Search for your country and DHS or MICS in Google, and you may find some valuable information about the lives of people in your country. You could use these surveys to see how access to WASH is progressing regionally, or by gender. If your government has promised to target the areas of greatest marginalisation, and share this information on WASHwatch under the box for Water Policy - Are there specific measures in the plan for targeting poor people, and addressing the interests of women?