[3] The Bureau of Economic Analysis (BEA) estimates that treating R&D as an investment increased the level of current-dollar GDP by an average of 2.5% per year during the period 1959 to 2002 (Okubo et al. 2006). The BEA estimate measures the direct impact of R&D and does not include the indirect (spillover) impact of R&D.

[4] GDP per capita does not reveal anything about comparative distribution of income across countries, for which data are not readily available.

[5] Extensive literature exists on the impact of IT on U.S. economic growth in the mid-1990s. For example, see Stiroh K 2001. What drives productivity growth? Economic Policy Review 7(1):39–59; Accessed 26 June 2007.