INFRASTRUCTURE AND GROWTH IN AFRICA compared to the role played by other structural factors and stabilization policies, and (b) we will assess the contribution of the different types of infrastructure stocks across African subregions and countries over the 15-year study period.

We conduct this analysis using both the [ **IK** 1] and [ **IK** 2a] aggregate indices of infrastructure stocks. Our results using our preferred aggregate index of infrastructure stocks, [ **IK** 1], are presented in tables 2 and 4 as well as figures 5 and 6. Note that the results for the other indices are presented (see table 5 and table A.3 in the appendix), although they are not discussed in the document. We should note that the results with these alternative indices are qualitatively similar to those presented with our preferred index [ **IK** 1].

# Infrastructure and other sources of growth in Africa

We perform an analysis of the sources of growth and we group the different determinants in the policy categories mentioned at the beginning of section 4. Although infrastructure development clearly belongs to the group of structural factors and policies, we consider it as a category by itself for the purposes of our analysis. In figure 5, we show the contribution of policy variables to growth in Africa (its subregions), as well as other regions in the world over the 15-year study period. Table 3 displays all the relevant information on the growth decomposition over time. We find that the model successfully predicts the changes in the growth of real output per capita in Western Europe, and does a fairly good job predicting changes in growth in some African subregions.

When we observe the results in table 3, we find that the contribution of infrastructure development to predicted growth is quite important in Western Europe and the EAP7. Infrastructure development contributes 99 basis points out of 1.1 percent predicted growth in the African region, while other structural policies contribute 68 basis points (mostly explained by improvements in education). Across subregions, the model predicts an increase in growth in Central Africa of 2.1 percent, with infrastructure development contributing with 1.08 percent (0.96 percent due to larger stocks and 0.13 percent due to improved quality). For Southern Africa, predicted growth increase in 2001–5 relative to 1991–5 was 1.2 (versus an actual growth increase of 2.2), and infrastructure development predicted an increase in growth of 1.01 percent (mostly attributed to higher stocks, which accounted for 0.85 percent), while other structural policies predicted an increase in growth of 0.55 percent.

Interestingly, West Africa is the only subregion where the contribution of other structural policies to growth (1.12 percent) is higher than the contribution of infrastructure development (0.88 percent) over the 15-year period. We should also point out that West Africa is the region with the smallest growth contribution due to infrastructure development. Among other structural policies, we find that the largest contribution to growth comes from improvements in education and institutional quality.

# The contribution of infrastructure assets to growth in Africa

We now decompose the contribution to growth of infrastructure development by infrastructure asset types. Figure 6 shows the contribution to economic growth in Africa of the different measures of infrastructure stock and quality in telecommunications, electricity, and roads sectors over the 15-year study period. For more detailed results, see table 4.

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