 The authors estimate that the main reason is the massive expansion of access to water, which was concentrated in poorer areas that did not receive services before private sector participation was introduced.The largest and best-known case of private sector participation in the Argentine water and sanitation sector was the Buenos Aires concession, signed in 1993 and revoked in 2006.Its impact remains controversial and in early 2008 an arbitration case was still pending with the International Center for Settlement of Investment Disputes (ICSID) of the World Bank Group.