years the company brought 24 hours service to all the city and served an additional 55,000 families, mostly low income in the southern part of the city. Access to water supply increased from 64 percent in 2000 to 72 percent in 2003, and access to sewerage has grown from 46 percent to 55 percent during the same period. According to an article written by Interagua for public relations all the "formally developed areas" of the city had access to piped water at "reasonable pressure" in 2012. However, according to Interagua's own annual report 2009-2010, only an estimated 82 percent of the population (almost 2 million out of a population of 2.43 million) had access to piped water and 67 percent had access to sewerage in July 2010. In 10 years access to piped water supply thus increased from 64 to 82 percent. Customers who gained access to piped water supply were able to consume twice as much water while paying one fifth of what they paid before, when they had bought it from vendors distributing it in tankers. Tankers charged US$ 3.50 per cubic meter, while Interagua charges only 34 cents per cubic meter for the first 15 cubic meters per month. The concessionaire also increased billing efficiency - the share of bills issued that are paid - to about 75 percent by 2003. The number of staff was reduced by 43 percent between 2001 and 2003. This brought the number of staff per 1,000 connections down to less than 3, a level that is consistent with international good practice for an efficient utility. Some of the remaining challenges are fluctuating water pressure and high levels of non-revenue water, consisting of both physical and commercial water losses. This is shown by the reports of the independent technical auditor who reviews annually the performance of Interagua. While the report confirmed that in 2010 at least 95 percent of all customers received water at a pressure above the minimum pressure, defined as 5 meters of water column (0.5 bar) in the center of the city and 8 meters of water column (0.8 bar) in the North of the city, the report contained no data about pressure variations and maximal pressure. Interagua wants to achieve constant pressure throughout its service area by 2015 or 2016. In 2010 the level of non-revenue water was 62 percent. This level is much higher than the average