"Rudisha is my role model, " said 18-year-old Nijel Amos of Botswana, who took silver.

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My model looks for firms with 10-year average ROEs of at least 15%, and 10-year ROTCs of at least 12%.

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It has made negative economic earnings (meaning its return on invested capital has been lower than its weighted average cost of capital) every year going back to 1998 when my model begins.

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