Of course in order that any change of rates should be reflected in prices, all carriers must of necessity agree upon the matter. The price is made by the least expensive source of supply. So that any carrier refusing to raise rates, might aid in the continuance of an already established price. Under conditions of transportation prevalent in the United States twenty years ago, the likelihood of an increased freight rate becoming a tax upon the community, was lessened by the probability that either by means of secret rebates, or by special and perhaps open commodity rates, some roads might choose to protect their clients against enhancement of prices. Markets were local--not reached by great systems operating from remote sources of supply. The policy of the northern transcontinental lines in making lumber rates from Oregon to the Middle West, might be quite independent of any policy in force on the southern hard pine carrying roads. But under present day conditions, the entire area of the United States is one great market. Hence, with rebates eliminated and with practical monopoly established through actual consolidation, control or harmony of policy, the carriers have the consumers much more completely at their mercy. Only two safeguards for the public interest remain. One is government regulation, or at all events supervision, of charges. The other is "enlightened self-interest"--which in transportation matters means a full appreciation of the possibilities and limitations in the application of the value of service principle to the determination of rates.