PRINCETON - Long viewed as an economic basket case, Sub-Saharan Africa is experiencing its best growth performance since the immediate post-independence years. Natural-resource windfalls have helped, but the good news extends beyond resource-rich countries. Countries such as Ethiopia, Rwanda, and Uganda have grown at East Asian rates since the mid-1990’s.

The question is whether this performance can be sustained. So far, growth has been driven by a combination of external resources (aid, debt relief, or commodity windfalls) and the removal of some of the worst policy distortions. Domestic productivity has been given a boost by an increase in demand for domestic goods and more efficient use of resources. The trouble is that it is not clear from whence future productivity gains will come.

The underlying problem is the weakness of these economies’ structural transformation. East Asian countries grew rapidly by replicating, in a much shorter time frame, what today’s advanced countries did following the Industrial Revolution. They turned their farmers into manufacturing workers, diversified their economies, and exported a range of sophisticated goods.

Little of this process is taking place in Africa. As researchers at the African Center for Economic Transformation in Accra, Ghana, put it, the continent is "growing rapidly, transforming slowly.”

In principle, the region’s potential for labor-intensive industrialisation is great. A Chinese shoe manufacturer, for example, pays its Ethiopian workers one-tenth what it pays its workers back home. It can raise Ethiopian workers’ productivity to half or more of Chinese levels through in-house training. The savings in labor costs more than offset other incremental costs of doing business in an African environment, such as poor infrastructure and red tape.

But the aggregate numbers tell a worrying story. Fewer than 10 per cent of African workers find jobs in manufacturing, and among those only a tiny fraction – as low as one-tenth – are employed in modern, formal firms with adequate technology. Distressingly, there has been very little improvement in this regard, despite high growth rates. In fact, Sub-Saharan Africa is less industrialised today than it was in the 1980’s. Private investment in modern industries, especially non-resource tradables, has not increased, and remains too low to sustain structural transformation.

As in all developing countries, farmers in Africa are flocking to the cities. And yet, as a recent study from the Groningen Growth and Development Center shows, rural migrants do not end up in modern manufacturing industries, as they did in East Asia, but in services such as retail trade and distribution. Though such services have higher productivity than much of agriculture, they are not technologically.

Consider Rwanda, where GDP has increased by a whopping 9.6 per cent per year, on average, since 1995 (with per capita incomes rising at an annual rate of 5.2 per cent). Xinshen Diao of the International Food Policy Research Institute has shown that this growth was led by non-tradable services, in particular construction, transport, and hotels and restaurants.

None of this is to dismiss Rwanda’s progress in reducing poverty, which reflects reforms in health, education, and the general policy environment. Without question, these improvements have raised the country’s potential income. But improved governance and human capital do not necessarily translate into economic dynamism. What Rwanda and other African countries lack are the modern, tradable industries that can turn the potential into reality by acting as the domestic engine of productivity growth.

The African economic landscape’s dominant feature – an informal sector comprising microenterprises, household production, and unofficial activities – is absorbing the growing urban labor force and acting as a social safety net. But the evidence suggests that it cannot provide the missing productive dynamism.

Optimists say that the good news about African structural transformation has not yet shown up in macroeconomic data. They may well be right. But if they are wrong, Africa may confront some serious difficulties in the decades ahead.

Two decades of economic expansion in Sub-Saharan Africa have raised a young population’s expectations of good jobs without greatly expanding the capacity to deliver them. These are the conditions that make social protest and political instability likely.

Dani Rodrik is Professor of Social Science at the Institute for Advanced Study, Princeton, New Jersey