But that, they argue, implies a mistaken reliance on factors such as natural resources, cheap wages or geographic location, and will not provide the basis for long-term prosperity.

ECONOMIST: Fish out of water

Due to widely varying country conditions, some African economies can take advantage of favorable wages and natural resources and benefit from taking timely measures to develop and export manufacturing goods.

CNN: Opinion: Could Africa be world's next manufacturing hub?

Ethiopia's comparative advantage in wages, productivity, and natural resources has led the Huajian Group, a Chinese shoe maker, to build a factory in Ethiopia in three months, with two production lines starting in January 2012, exporting 20, 000 pairs of shoes a month and creating some 550 jobs.

CNN: Opinion: Could Africa be world's next manufacturing hub?

They cannot help wondering why, with its educated population and bountiful resources, including the world's second-largest reserves of both oil and natural gas, Iran struggles with high unemployment, low wages and surging inflation.

ECONOMIST: Iran gives America the finger

The traditional reasons given for the higher natural rate of unemployment are better social security, stricter labour laws, minimum wages, lower labour mobility, and some others.

FORBES: Is There Hope For Employment In Europe?

But anticipating more recent work, Mr Phelps, the theory's other pioneer, has long emphasised the need for measures to lower the natural rate--essentially, by making more people employable at the prevailing level of wages.

ECONOMIST: Up the NAIRU without a paddle