 environmental protection and natural resource management. These factors are expected to add significantly to the costs incurred in the supply of water services and wastewater treatment. The projections indicate that as we progress through the next three decades, water-related infrastructure investment requirements are likely to grow significantly and could well dwarf the requirements in the other three sectors under investigation by 2020-30. This suggests that governments will need to pay particular attention to water in the future - not only because, like air or food, it is essential for life, but also because investment outlays will be huge throughout the world. Total investment across all infrastructures On the basis of the estimates provided in each of the sectoral chapters, it is possible to provide an overview of the findings on likely global infrastructure investment requirements through to 2030. These are presented in tabular form below. However, it is important to bear in mind not only the caveats spelled out at the beginning of this section, but also the fact that the projections for each sector have been developed on the basis of different approaches, different methodologies and different data sets. Hence, the table INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISBN 92-64-02398-4 - © OECD 2006 A CROSS-SECTORAL PERSPECTIVE ON THE DEVELOPMENT OF GLOBAL INFRASTRUCTURES TO 2030 can only provide an indication of the orders of magnitude of the infrastructure investment requirements worldwide over the next few decades. Moreover, the figures reflect needs, which for many different reasons may not necessarily translate into effective demand. Table 1.1. Estimated average annual world infrastructure expenditure (additions and renewal) for selected sectors, 2000-30, in USD Bn and as a percentage of world GDP Approximate % Approximate % Approximate % Type of infrastructure 2000-10 2010-20 2020-30 of world GDP of world GDP of world GDP Telecoms ¹ Electricity2 Water1 3 1. Estimates apply t