After making similar allowances for skills and experience, the World Bank reckons that union membership increases a South African worker's wages by 25-35%, a much higher differential than is found in other countries.

ECONOMIST: South Africa

German efficiency and once-matchless engineering can reduce that differential and justify higher prices, but only to a degree.

ECONOMIST: Germany's economy

Note: at higher income levels, this differential will be less significant, but still results in a tax savings by delaying.

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Some of that cost differential could be offset by higher productivity and greater labour flexibility in western countries.

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When the differential is in positive territory (red) it means higher, stronger air over the North Atlantic pushes up on the low-pressure air over the Arctic circle.

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Differential tuition is a variant of performance-based funding, a system of allocating state higher education resources based on performance metrics such as degree completion.

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