The different levels of water tariffs across cities (Figure 3.13) suggest that there is scope for increasing tariffs and the derived revenue in many municipalities. But there is also scope for increasing revenue (as well as the incentive effects of water pricing) from enhancing billing and collection of water tariffs. In 2010, water operators collected 81% of the MXN 35.5 billion billed to their clients (CONAGUA, 2011c), down from a peak of 89% in 2008. This means that MXN 6.7 billion were not collected. In ten Mexican states, water operators collect 95% or above of the amounts billed (see Figure 3.15).