Concerns about the nation's infrastructure and its ability to support commerce and promote public well-being have prompted calls for greater infrastructure spending. In response to a request from the Chairman and Ranking Member of the Senate Committee on Finance, the Congressional Budget Office (CBO) prepared this study, which analyzes recent developments in spending on transportation and water infrastructure, trends in spending for capital and for operations and maintenance by the various levels of government, and the rationale for public spending on infrastructure. This study updates a 2007 report, Trends in public spending on transportation and water infrastructure, 1956 to 2004--Preface.