The Millennium Development Goals (MDGs) have passed their target year, and are followed by the Sustainable Development Goals. One of the achieved MDG targets was halving the proportion of the Population without sustainable access to safe drinking water. In the course of the MDGs, how and why was the target achieved, and what contributed to the achievement? It was revealed that the major contributors to the achievement of the target were China and India, and that the increase in the proportion of population with access to improved sources was closely associated with economic development in most nations during 1990–2015.