The phosphate fertilizer industry is always changing due to shifts in supply and demand. Farmers' decisions on how much fertilizer to buy are influenced by the expected return on investment. In the United States and Western Europe, phosphate fertilizer use has been steadily increasing over the past few decades. When wheat prices dropped in the late 1960s, fertilizer use also decreased in regions where wheat is a major crop. This shows a clear link between fertilizer consumption and world grain prices.