Africa is not a monolith - there have been economic success stories and catastrophic failures. It is true that on the whole no country in Africa has seen the consistent long-term growth that China has seen (while some have achieved high single digit growth for short periods), but we should keep in mind that very few countries have. The club of countries whose growth rates have averaged above 7% for more than 3 decades includes just five countries: Japan, Taiwan, South Korea, Singapore, and the People's Republic of China. It would be helpful to look at this from another angle - what enabled those countries to achieve what the other 175-odd countries in the world have not.

Throughout human history, stagnation has been the norm and development the exception. Rapid development is even more of an exception. From 5,000 BC to 1700 AD, GDP per capita growth in all regions averaged zero. In other words, a French farmer in 1600 AD was no richer than a Gallic farmer in the time of the Roman Empire. Technology did advance, but was always outpaced by population growth. Once stable banking institutions were created, education increased, and fertility declined (mostly as a result of increasing education), the rate of technology growth exceeded population growth for the first time, leading to what contemporaries labelled the "Industrial Revolution".

Just how fast was this "revolution"? Until WW2, most "industrializing" countries averaged a per capita growth rate of around 1%, with Austria Hungary's 1.70% growth rate before WW1 being considered "extremely fast". The United States and Meiji Japan both averaged 3%. This is a fairly normal growth rate today, but to contemporary observers it was miraculous.

Consistent rapid growth did not become a possibility until 1945, when Japan innovated a growth model which would later be copied by its larger neighbor. That year, the American occupation authorities in Japan conducted a comprehensive purge of the pre-war Japanese political elite - including politicians, corporate executives, and military officials - but ignored the bureaucracy, who held the real power in Japan. In the Ministry of Munitions, more than 90% of staff were allowed to keep their posts. This put Japan firmly under the control of a well-educated, technocratic elite who for decades had been experimenting with novel economic ideas.

In pre-war Japan, there existed an eternal political battle between bureaucrats and the zaibatsu - large, family owned corporations. The zaibatsu subscribed to mainstream economic ideas at the time and favored non-intervention in the economy for reasons that should be obvious. Bureaucrats, in contrast, lamented Japan's continued state as a semi-industrialized, semi-impoverished country and favored a more decisive policy towards industrialization. Experiments headed by bureaucrats Kishi Nobusuke in Japanese-occupied Manchuria and Finance Minister Takahashi Korekiyo in Japan were successful in granting Japan a uniquely rapid recovery from the Great Depression, and influenced post-war policy.

Once the Americans dissolve the zaibatsu, Japanese bureaucrats seized control of the private sector by rebuilding the zaibatsu around their savings banks, and restricting the power of shareholders over management. The savings banks were in turn controlled by a system pioneered by the Bank of Japan, which mandated a high reserve ratio (the % of bank funds that have to be stored in the central bank) but liberally lent out money to the banks, keeping them cash-poor and dependent on the bank. Loans were then channeled through the banks to government-favored projects through a policy first known as "priority production" and later refined into "strategic sectoring". Under this policy, sectors that the government favored would receive free land, a faster rate of asset depreciation for tax purposes, foreign currency injections for the purchase of foreign technology, and sales tax exemption for domestic sales. This naturally meant any banker or corporation wanting to make money paid close attention to government memos.

Sectors designated as strategic were chosen because of their income elasticity. Elasticity is the degree to which product demand rises as consumer income rises - the production of these tended to have a multiplying effect on growth, as industries became more profitable as the country continued to grow. At the same time, the government embarked on numerous projects to reduce industrial costs, including dredging new ports and mandating that "strategic" factories build next to the harbor to reduce shipping costs. Finally, the government undertook a number of measures to increase the domestic savings rate, including offering a tax exemption on deposits to the Postal Savings Bank.

As you can see, none of this was simple or straightforward, and some of it was very counterintuitive. The idea that the state knew better than private corporations in some circumstances was especially controversial according to both pre-war and post-war economic theory. Critically, Japan, and later China, exploited the interaction of high growth rates and income elasticity to make state-sponsorship effective.

The Chinese growth model closely imitated that of Japan, with economic decision making relatively more concentrated at the local level. All provinces in China are heavily encouraged to subsidize the production of coal and iron to reduce the cost of steel. Local governments and the national government over the years have given several sectors special privileges including free land, tax benefits, and foreign currency to seek technology transfers over the years. All these sectors - ranging from automobiles to consumer electronics - produce goods with high income elasticity. China's four major state banks act in the same fashion as the Bank of Japan, providing a virtually unending stream of credit to local governments and companies (private and public) that invest in sectors the state has deemed a priority. These loans are facilitated, as in Japan, by government policies designed to increase the savings rate.

All this begs the question - why don't other countries imitate the same model? First, there are institutional barriers that prevent a perfect replication. Developmental economics is mired in constant ideological battles between proponents of state and market driven approaches. In the 1980s and beyond, the International Monetary Fund and World Bank promoted a development strategy that made foreign funding conditional on institutional reforms that weakened state power in economic planning. In much of sub-Saharan Africa, foreign aid makes up more than a third of government budgets and governments have little choice but to negotiate their development strategies with foreign institutions. Second, there are internal barriers. What Japan, South Korea, and China all share in common is that, just prior to introducing an effective development strategy, all three endured sweeping political purges. As mentioned, most of the Japanese pre-war elite were removed by occupation authorities. In South Korea, Park Chung-hee eradicated much of the old guard following his coup. In China, the Mao-era elite were devastated both by the Cultural Revolution and by Deng Xiaoping's counter-revolution. What remained in all three countries was a strong central government with little opposition, few political "mouths" to feed, and national governments whose primary political priority was strength through development. In many countries, state-directed growth has led to nothing but stagnation and the continued subsidization of inefficient and noncompetitive industries, because those industries are important for maintaining the support of certain players or constituencies. Put simply, in many countries, corruption and inefficiency are necessary, and therefore an expanded state role in the economy is unlikely to produce results.

In summary, many African countries are growing at respectable and even fast rates. As a continent, Africa's growth has averaged around 4% a year over the past decade, which is not slow by any means. High-speed growth is an extremely rare exception in history, not a rule. It requires adherence to a still-obscure and counter-intuitive development strategy, a government with few decision makers to "pay off", and decades of financial discipline.

Sources:

Yang, Yao. The political economy causes of China’s economic success. <A good overview of competing hypotheses in China's growth that debunks "cultural" and determinist hypotheses>

Lin, Yifu. Demystifying the Chinese Economy.

Landry, Pierre et al. Does performance matter? Evaluating political selection along the Chinese administrative ladder.

Johnson, Chalmers. MITI and the Japanese Miracle.

Lin Yifu et al. The China Miracle. <One of the founding works on the study of China's political economy and one of the first works to seriously analyze the role of the state in development instead of just analyzing "reforms">

Yang, Yao. Heavy industry and economic development: The Chinese planning economy revisited.

Kenderdine, Tristan. China's Industrial Policy, Strategic Emerging Industries and Space Law.

Maddison, Angus. Maddison project growth data.

African Economic Outlook 2017.