In the case of countries that are abundant in metals and minerals, growth per worker was cut from an average annual rate of 0.6 percent in 1961-77 to -3 percent in 1978-96. The plunge in output per capita was driven not only by a reduced contribution of physical capital but also a sharp drop in TFP growth. During the period 1996-2014, growth per worker accelerated to 0.9 per year —with human capital and TFP growth contributing to this increase in the growth of labor productivity.<sup>4</sup> Finally, the growth rate of output per worker among non-resource rich countries contracted 0.4 percent per year during the 1978-95 period (down from 1.7 percent per year in 1960-77). Both physical capital and TFP growth contributed negatively to the deceleration in the growth rate of output per worker. During the period 1996-2014, growth per worker recovered to 2.3 percent per year for this group. About three-quarters of the observed growth per worker was attributed to the accumulation of physical capital and human capital (1 and 0.7 percent per year, respectively) while the remainder was explained by TFP growth (0.6 percent per year).

Considering that an important number of countries in the region are rich in natural resources, it is only logical to ask what the contribution of that factor of production to the sources of growth is. Figure 4 reports the growth decomposition during the period 1996 – 2014 that incorporates the stock of natural resource wealth as an additional input —specifically, another type of capital good. Recent methodological developments have allowed us to include natural capital in the measurement of TFP —which is particularly relevant for natural resource rich countries in the region. Growth accounting methodologies include natural resources as an additional factor of production (e.g. Brandt, Schreyer and Zipperer 2017, Monge-Naranjo, Sánchez, and Santaeulalia-Llopis 2017). Additionally, there is greater coverage and quality of the data on natural resources —especially, the value of the natural wealth associated to energy commodities (coal, petroleum, and natural gas), mineral ores and metals (Lange et al. 2018).

The data on the stock of natural capital in extractive industries (petroleum, natural gas, coal, minerals and metals) are available only for the period 1996-2014. Additionally, the inclusion of natural capital in the growth decomposition restricts the country coverage in Sub-Saharan Africa from 44 (Figure 3) to 37 (Figure 4) countries. However, the excluded countries are not representative in size relative to the entire group: the seven Sub-Saharan African countries without data on natural resource wealth amount to less than 0.5 percent of the region’s population.

The decomposition of growth in real output per worker into physical capital, natural capital, human capital, and TFP growth is depicted in Figure 4. Natural capital is defined in this paper as the value of the capital associated to energy (petroleum, natural gas, hard and soft coal) and mineral resources. The data are collected from Lange et al. (2018). The accumulation of physical and human capital explains 70 percent of the observed growth per worker observed in Sub-Saharan Africa in the period 1996-2014 (1.1 and 0.6 percent per year, respectively) whereas natural capital explains about 20 percent (0.5 percent per year). Finally, TFP growth contributes with 10 percent of the observed growth per

> 4 Two observations emerge from the analysis of Figure 3: (a) international commodity prices appear to be connected to the growth and productivity fortunes and misfortunes of both groups of resource rich countries. (b) We have to take the TFP growth calculations with caution as omitted variables (e.g. natural resource wealth for resource rich countries) may misrepresent the contribution of TFP to growth per worker.

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