In recent years, demand and price for several important agricultural commodities—notably rubber, jute, hard fibres and cotton—have been depressed by the development of synthetic substitutes. Synthetics have been encouraged by periods of scarcity or relatively high price for the natural product. The heavy outlay in the manufacture of synthetics is in the initial construction of the plant: after that, marginal costs of production are quite low, so that the makers of synthetics can, if necessary, compete with the natural product down to rather low prices.