US trend), we would have to assume that only 30% of "new construction" is a net addition to the road capital stock. This latter result would indicate that while 50% of road spending might be on new construction, only a third of this (15% of overall road spending) might be a net addition to the capital stock. Another way of stating this is that for every USD 1.00 net addition to road capital stock, it may be necessary to spend USD 6.67 (i.e. 1/6) on roads, or about USD 3.33 on "new construction". 12 The Fay-Yepes approach did estimate components for both net-additions to the capital stock and for maintenance, with only a slightly higher amount of maintenance (60%) relative to net additions (40%). Our analysis suggests that the maintenance component may need to be much greater (by a factor of 2) in the future. In the Fay-Yepes approach, a two-tiered set of capital stock responses is used: For high-income countries (HIC), based on panel data (pooled cross-section and time-series), the elasticity of paved road asset value (i.e. infrastructure stock) with respect to GDP per capita is 0.23. For low-medium-income countries (L/MIC) the elasticity is 0.14. 13 Using these relationships, a world paved road new construction estimate of about USD 260 billion/year was made by Fay-Yepes (see Table 4.2) for the period to 2010 - which involved annual infrastructure growth of about 1.6% for high- income countries, 2.3% for medium-income countries, and 1.4% for low-income countries. 14 The new construction figure was comprised of USD 116 billion of net addition to the capital stock, and road replacement capital investment of about USD 143 billion/year. As will be seen in Section 2, our comparable (perhaps more involved) methodology is fully consistent in terms of order-of-magnitude with these forecasts. 15 Besides a careful review of and modifications to the underlying methodology, this model has the advantage of extending the analysis beyond 2010 to 2030. INFRASTRUCTURE TO 2030: TELECOM, LAND TRANSPORT, WATER AND ELECTRICITY - ISB