The PROTAR (Wastewater Treatment Program) programme prioritises wastewater treatment works that belong to inter-municipal systems and does not provide support for rehabilitating a work before five years. Investments to increase efficiency increased (in constant 2008 prices) from 2002-2008 from MXN 1.5 billion to MXN 4.0 billion (CONAGUA, 2011c). However, this only represents an increase from 11.5% to 13.6% of the total sub-sector investments.