 public health. And thirdly, in the field of nanotechnology, advances are likely to have the greatest impact on maintaining and enhancing the performance of infrastructure. This could come about through the use of sensors, smart materials and materials with the ability to self-heal and regenerate. 3. The outlook for infrastructure investment requirements This section provides an overview of the projections presented in each sectoral chapter and gives a brief outline of the basis on which they were made. To begin with, however, a few cautionary remarks are in order. It is important to note that the purpose of long-term projections is not to forecast the future. Rather, it is to explore how the future might evolve given a set of economic, social, technical and political assumptions, among these usually the absence of any new policy actions. Despite the uncertainties naturally attached to such long-range projections, experience has shown that they offer a useful framework for identifying critical factors and for reflecting on the policy levers that could be used to steer the economy and society at large towards a more desirable future. Moreover, consideration of the major shaping INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISBN 92-64-02398-4 - © OECD 2006 1. A CROSS-SECTORAL PERSPECTIVE ON THE DEVELOPMENT OF GLOBAL INFRASTRUCTURES TO 2030 factors can also help governments identify some of the policy levers that could be applied in pursuing objectives. With this in mind, the findings of the sectoral chapters should be treated solely as indicative of the order of magnitude of the investments that are expected to be required. Telecommunications Annual total infrastructure spending worldwide is expected to rise from USD 650 billion in 2005 to USD 745 billion in 2010, falling thereafter to USD 646 billion in 2015, USD 572 billion in 2020 and USD 171 billion by 2025. After a period of rapid expansion of capacity (notably in developing countries) in the initial phase, the sharp reduction toward