Data from measurement firm Experian PLC show retail foot-traffic down in West London, sometimes substantially, for nearly every day of the games.

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But even by this suboptimal RVU-based measure, there are a number of well-done studies that all show that productivity declines, sometimes substantially.

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In a down market, these same bond ETFs may trade below NAV, sometimes substantially, when there are more sellers than buyers and market makers are unwilling to bring the ETFs back to NAV.

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