Studies show a correlation between more women in senior positions and superior company performance, though it is hard to know whether more sexual diversity improves performance or top-notch firms promote more women.

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Therefore, investors need to know whether paying more will increase the likelihood of superior performance.

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The higher the fees, the more difficult it is to achieve superior net investment performance.

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Maybe you will decide that the amount spent on US universities is a consequence of their superior performance - that is, people pay more because they perceive US university education to be better - so spending follows performance rather than causes it.

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Third, Mr. Brill completely ignores some far more appropriate metrics on which U.S. performance is superior.

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Offering superior performance with a fast CPU to simultaneously support multiple user streams, more memory to boost performance, four drives for up to 16TB of storage, and two Gigabit Ethernet ports for high speed data transfer and failover, the Cloud Storage 4000 is a robust storage, back-up and recovery solution.

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America's superior performance owes a lot to structural reforms in the late 1970s and 1980s that created a more favourable climate for business, allowing firms to reap the benefits of new technology.

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