One way in which this is true is simply that the World Cup matters for share prices. The MIT's Alex Edmans and colleagues have shown than when a country is knocked out of the tournament, its stock market subsequently falls. This confirms that share prices depend not just upon 'fundamentals' such as profits and interest rates, but also upon sentiment.
Guy Kaplanski and Haim Levi, two Israeli economists, believe investors might be able to profit from this effect even if they cannot predict the outcome of games. Their reasoning is cunning. As investors get depressed by their team's failure, they say, they'll sell not just their domestic stocks but some US ones too. And because 31 of the 32 national teams will lose at some stage, the overall effect upon the US market will be negative. Sure enough, they show that, on average, US share prices do significantly worse during World Cups than they do at other times. They estimate that the US stock market underperformed cash during 12 of the 15 World Cup tournaments between 1950 and 2006. Although their paper was written before the 2010 World Cup, that one fitted their pattern, as the S&P 500 fell slightly during it. In this sense, going short of the S&P 500 during the World Cup might make money.