http://www.who.int/water_sanitation_health/monitoring/jmp2005/en/
http://www.who.int/water_sanitation_health/waterforlife.pdf/

It presents the report published by the WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation, it makes clear that achieving the target of the Millennium Development Goals (MDG's) for access to safe drinking water and basic sanitation will bring a payback worth many times the investment involved.