a previous estimate of 0.4% of GDP for middle-income countries. Adjusting the 2% of GDP to reflect the differences they note between high-, middle- and low- income countries indicates that the amounts to be spent on new infrastructure and maintenance would be 0.4% of GDP for high-income countries, 1.9% for middle-income countries and 2.5% for low-income countries. However, there is some ambiguity in the published figures. In the following sections examples of the investment requirements for certain OECD and other important countries are discussed on the basis of present trends. United States The major factors driving capital investments are regulatory compliance, growth and the age of the infrastructure, accounting for 7%, 40% and 30% of expenditure (Brow, 2001). However, these figures reflect expenditure rather than INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISBN 92-64-02398-4 © OECD 2006 5. THE IMPACTS OF CHANGE ON THE LONG-TERM FUTURE DEMAND FOR WATER SECTOR INFRASTRUCTURE need. Various estimates of the required levels of expenditure have been made in recent years (Table 5.10). These have included the EPA's periodic "needs survey" of drinking water and wastewater systems, estimates by the Water Infrastructure Network (WIN) and the American Water Works Association, and the Congressional Budget Office. The Water Infrastructure Network report (WIN, 2000) estimated that drinking water utilities need to spend USD 24 billion per year for the next 20 years on infrastructure but that currently the expenditure is USD 13 billion per year. For wastewater systems the figures are USD 22 billion and USD 10 billion per year respectively, leaving an overall gap of USD 23 billion per year over 20 years (Johnson, 2004). These amounts dwarf the existing level of funding, and federal subsidies used to supplement user fees and help finance capital investments are unlikely to address the real causes of inadequate maintenance: the institutional arrangements and managerial practices (Levin et al., 2002).