Speculative markets such as those for stocks or currencies typically have an extremely short time horizon for transactions. Yet at the same time, stock prices and exchange rates go up or down in trend curves of several years ("bull" and "bear" markets). The paper takes the dollar/euro exchange rate to study how short-term price movements accumulate to produce long-term trends. It found that speculative prices fluctuate around "underlying trends". The "trending" phenomenon repeats iself along a range of time scales. Long-term trends develop from the accumulation of price waves based on daily rates which continue longer in one direction than the other across several years. A succession of such trends produces a pattern typical for the long-term dynamism of speculative prices: they vary in irregular cycles across a factual balance range without inclining to converge towards that balance.