authorities are responsible for roads, highways, and bridges, while subways, ports, airports, and railroads are owned and operated by quasi-public or private organizations. Overlaid on these organizations are institutions responsible for developing standards and enforcing compliance with regulations for critical infrastructure systems.

All of these systems and their components have finite lives. Their condition and performance inevitably deteriorate over several decades of use. For their service lives to be extended, these systems require reinvestment through timely maintenance and repair. Eventually they require replacement, in whole or in part.

In 2004 alone, public and private expenditures on critical infrastructure systems totaled $285 billion (Table 3.1). However, these investments have not kept pace with infrastructure needs. The American Society of Civil Engineers, for example, estimates that $2.2 trillion are required over a 5-year period to bring the nation’s infrastructure to a good condition that meets the needs of the current population (ASCE, 2009). Studies for the Federal Highway Administration, the Federal Aviation Administration, and other agencies report that about $20 billion more are needed annually to keep transportation services at today’s levels—levels that are already inadequate in some areas of the country (CBO, 2008). Another report estimates that the electric utilities industry will need to make a total investment of at least $1.5 trillion between 2010 and 2030 to keep pace with demand (Chupka et al., 2008). The Congressional Budget Office has estimated that an average annual investment of $24.6 billion to $41 billion is needed for drinking water and wastewater systems for the years 2000 through 2019 (CBO, 2002).

Although the needs are great, public investment in infrastructure has declined substantially as a portion of the gross domestic product for the past 50 years (Figure 3.1).

Even before the 2008 financial crisis, the U.S. Government Accountability Office projected that net interest on the national debt, Social Security, Medicare, and Medicaid would consume an increasingly large portion of the federal budget through 2040, limiting the funds available to meet the nation’s critical infrastructure challenges (GAO, 2006). Although the 2009 economic stimulus package contains some funding for infrastructure improvements, over the long term the resources available to renew and restructure infrastructure systems and their compo-



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