The intricacy of freight rate adjustment in response to the subtleties of commercial competition depends only in small measure upon the absolute freight rate imposed. The main problem is really that of relativity. But this does not mean mere relativity as between directly competing commodities or places. A strict relativity based upon commercial conditions must often obtain as well between the rates on raw materials and their own finished products; between all the various by-products in an industry; and, of course, always as between goods capable of substitution one for another. A few illustrations will serve to make these details clear. The matter of properly correlating the freight rate on raw materials and the finished products made from them, is more far-reaching than it seems. The location and development of manufacturing depends upon it. The country may be broadly divided into agricultural and manufacturing sections. The first of these is ambitious to develop its resources; not only to feed, but to clothe itself and make other provision for its needs. No sooner does it seek to develop local manufacturing than it finds itself exposed to competition from the older established manufacturers at a distance. Sometimes, even, these remote manufacturers draw their supplies of raw material from its own fields and forests. These supplies are then shipped long distances as raw material; manufactured and thereafter returned to sell in competition with the local product. The local market in relatively undeveloped areas is probably insufficient to provide support for manufactures on a profitable scale. It is essential to dispose of the surplus product over a wider area. Thus there arise two classes of manufacturers: one "next the stump," manufacturing at the source of the raw material and desiring to ship the finished product; the other, remote perhaps from supplies of raw material, but favored by long experience, by abundant supplies of capital and of skilled labor and by other advantages.[108] Neither class of shippers can prosper without overflowing into the domain of the other. The outcome of this competition depends in part upon the policy of the carriers. If the rate on the raw material be relatively low, the remote manufacturer is aided. Cotton mills and shoe factories in New England prosper in competition with establishments in the South or the Middle West. If, on the other hand, the rate on raw materials be inordinately high, while at the same time low on outward-bound shipment of manufactures from the seat of the raw materials, the tendency is in favor of the upbuilding of manufactures, not near the historic centres of population and consumption, but near the sources of natural wealth, which are the potential homes of manufacturing.