 Additionally, a strong nationwide increase in access to improved sanitation (64% to 85%) was observed in the same period.Other achievements include the existence of a functioning national system to finance water and sanitation infrastructure with a National Water Commission as its apex institution; and the existence of a few well-performing utilities such as Aguas y Drenaje de Monterrey.The challenges include water scarcity in the northern and central parts of the country; inadequate water service quality (drinking water quality; 55% of Mexicans receiving water only intermittently according to results of the 2000 census); poor technical and commercial efficiency of most utilities (with an average level of non-revenue water of 51% in 2003); an insufficient share of wastewater receiving treatment (36% in 2006); and still inadequate access in rural areas.