law, the latter would not be so effective in promoting monopoly. Speaking generally, we may say that when a great corporation controls a large proportion of the raw material entering into its manufactured products, such control will supplement and reinforce very materially those other special advantages which make for monopoly.[57] Prominent examples are to be found in steel, natural gas, petroleum, and water powers. In his "Report on Water Power Development in the United States," the Commissioner of Corporations (March 14, 1912) declared that the rapidly increasing concentration of control might easily become the nucleus of a monopoly of both steam and water power. Ten great groups of interests, he said, already dominated about sixty per cent. of the developed water power, and were pursuing a policy characterised by a large measure of agreement.[58] As a rough generalisation, it would be fair to say that in one or two instances, at least, landownership is the chief basis, and in several other cases an important contributory cause of monopoly. Even an approximately accurate estimate of the amount of money which consumers are compelled to pay annually for the products of such concerns over and above what they would pay if the raw material were not wholly or partially monopolised, is obviously impossible. It may possibly run into hundreds of millions of dollars. _Excessive Gains from Private Landownership_ The second evil of private landownership to be considered here, is the general fact that it enables some men to take a larger share of the national product than is consistent with the welfare of their neighbours and of society as a whole. As in the matter of monopoly, however, so here, Single Tax advocates are chargeable with a certain amount of overstatement. They contend that the landowner's share of the national product is constantly increasing, that rent advances faster than interest or wages, nay, that all of the annual increase in the national product tends to be gathered in by the landowner, while wages and interest remain stationary, if they do not actually decline.[59] The share of the product received by any of the four agents of production depends upon the relative scarcity of the corresponding factor. When undertaking ability becomes scarce in proportion to the supply of land, labour, and capital, there is a rise in the remuneration of the business man; when labour decreases relatively to undertaking ability, land, and capital, there is an increase in wages. Similar statements are true of the other two agents and factors. All these propositions are merely particular illustrations of the general rule that the price of any commodity is immediately governed by the movement of supply and demand. In view of this fact, it is not impossible that rent might increase to the extent described in the preceding paragraph. All that is necessary is that land should become sufficiently scarce, and the other factors sufficiently plentiful.