FX markets are to an extent, yes, relevant to an economy's overall performance. If the Japanese economy starts to perform better than the United States, the value of the Yen will in theory increase relative to the US Dollar. This generally is indicative only on a very large scale. This traditionally means that foreign currencies' value is relative to increases/decreases to their economic weight. If the Australian economy were to tank at the same time the US economy were making leaps and bounds, AUD/USD would fall in value.