The currency problem is an issue. I live in Norway and trade in the US. In 2001 I got close to 900 NOK for every 100 USD. Today the exchange rate is 680 NOK for 100 USD. Kroner have appreciated almost 25% in that period (and the dollar plummeted). That means I have to trade 25% better to make the same amount of money.....
hedge my dollar/pound risk.