Inventions often shift demand, and value follows. The invention of the bicycle with pneumatic tires, coincident with the adoption of electric traction for street cars, reduced the price of horses between 1890 and 1895. This doubtless was a factor in agricultural land values at that time. This change was sudden, extreme, and temporary, and there has since been a gradual adjustment and a return to the former values. [Sidenote: Consumers' choice as affecting productive forces] 3. _The production of the next period may be radically affected by the use now made of agents._ Some consumption takes the form of using up and reducing the stock of wealth. The demand for lumber causes the disappearance of the forests, whereas the demand for oranges stimulates the planting of orange trees. The reckless exploitation of natural resources leaves society poorer. Great herds of buffalo were slaughtered to get the hides, which were of comparatively slight value. Rich land has been exhausted to get a few harvests. War is a use of wealth for ends believed at the time to be necessary and believed to forward social welfare better in the long run than would dishonorable submission; but it causes misery and leaves industry prostrate. The forms taken by saving are affected by the choice of expenditure. In war the savings of individuals are given to the government and used for destructive purposes. The lender parts with his wealth and society uses it up. While the lender has a claim on the industry and on the remaining property of the community, society as a whole is the poorer. If the savings had taken the form of public buildings, libraries, railroads, and factories, the wealth and income of society as a whole would have been enhanced. [Sidenote: Consumers' choice as affecting wages] 4. _The kind of consumption affects the wages of the various classes of labor._ That an increase in the supply of a given grade of labor reduces its wages and encourages its use, and vice versa, is a truth that became familiar in the study of wages. An influence also is exerted from the side of goods upon the price of labor. A shift of demand from one kind of goods to another depresses the wage of the one kind of labor and raises that of the other. A low grade of labor that performs only simple tasks, and those but badly, is injured if demand shifts to better products. Back of the sweat-shop shirt is the problem of the inefficient worker. Progress takes place by the effort of labor to increase its efficiency and to move into higher paid callings, and at the same time by the desire of the purchaser to buy as good a quality as he can. [Sidenote: The consumer's responsibility]