The diversification effect that comes from investing in countries with low cross-correlations can result in both an increase in return and a reduction in volatility at the total portfolio level over the long term.

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The cross-state provisions were enacted in July 2011 and they were to take effect in January 2012.

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Cross-country skiing also employs a second form, kick wax, which has the opposite effect.

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This can then be cross-matched against things like online sales or search advertisements, and actions taken to see what further effect these might have on product sales.

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This has been done, but it is unsatisfactory because in a cross-country comparison many other things vary along with political institutions: it is impossible to isolate the effect of political arrangements on happiness.

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