Over the course of mid-2014 to mid-2015 global wealth has increased at a good rate. This growth has been driven by the United States and China. In other geographies any local currency wealth gains were offset by depreciation against the US dollar to such an extent that world wealth declined overall by $12.4 trillion. In the absence of this adverse exchange rate movement total global wealth would have risen by $13trn.
US investors who take a globally diversified approach with their portfolio have suffered in a similar fashion due to this dollar strength. Investing via the US dollar in non-US markets has clipped returns from regions such as Europe and Asia. It is hard to protect oneself against such fluctuations in exchange rates, one must console oneself with the fact that over an investment time horizon sometimes currency will help you and sometimes it will hurt you, but ultimately it is a zero sum game.