_Normal value._—In this way the cost of production is said to fix the normal value of any article of commerce capable of production in indefinite quantity and within limited time. For this reason farmers are interested in finding the average cost of production of wheat, corn, etc., within a region supplying their market. They are even interested in knowing the conditions for wheat raising in India, South Africa and Australia, since the cost of production there may influence the value of wheat throughout the world. The normal value of products capable of indefinite multiplication tends always toward the value of the least costly. This is shown in the effect of labor-saving machinery upon the value of cloths and other goods. It is equally true in agriculture that wheat raising upon cheap land with extensive use of machinery and economical methods of culture and harvesting brings down the normal value. So long as more land can be applied to wheat raising with these advantages, the less productive methods may be too costly for the market. On the other hand, if any production cannot be largely extended so that the supply in market barely meets the requirements of purchasers, the tendency of normal values is toward the cost of the most costly part of the product required to meet wants. This is because the supply is kept up only by the exertion of the greater amount of labor as well as the less. If farmers in western prairie country can raise corn at an expense of 15 cents per bushel, as they can upon an average, so long as that region can raise all the corn required no less productive region can force the normal price above what will keep western farmers raising corn. When the western crop fails, the price is far above normal value, and may even go above the cost of the most costly corn in market, under a principle called the law of supply and demand.