The simplest compromise in any dispute over rates between competing centres is the concession of absolute equality or, as it is called, of flat rates between all points irrespective of distance. This shifts the burden from the carriers and places competition entirely upon the shoulders of the merchants. Oddly enough, also, this result of equal rates regardless of distance between various competing centres, especially when they are secondary distributing or concentrating points rather than original sources of traffic, may sometimes evolve naturally out of commercial conditions imposed by tariffs built up upon the basis of distance. The accompanying theoretical diagram, based upon actual traffic conditions prevalent in Missouri river territory, serves to illustrate the way in which, under certain circumstances, such equalization of rates may take place. Two groups of cities are here represented as though lying respectively along two river valleys north of their separation at a point G. Let us call them the Mississippi and the Missouri for purposes of identification. The starting point is equality of rates from such a distant point as New York (O) to all places along the Mississippi from A to G. Such equality properly arises in theory from the substantially equal distance from New York. In practice also, under the trunk line rate system,[98] such equality prevails, inasmuch as the rates from New York to such a series of Mississippi river crossings is fixed at 125 per cent. of the rate from New York to Chicago. By a similar course of reasoning, namely, the approximately equal distance from New York (O), rates from that place to a second series of points along the Missouri river should be and are in effect made equal. From these two facts it logically follows that the balances of the rates from all points on the Mississippi river out along an extension of their lines from New York toward the west should also be equal. This is obviously in conformity with the mathematical principle that equals subtracted from equals leave equal balances. Thus the rates B X, D Y and F Z are compelled to equality. From this relationship in turn follows still another. All rates from any point on the inner series of towns to any point whatsoever on the outer western series of places along the Missouri river must remain equal regardless of distance. For each line from New York to A, B, C, D, etc., wishes, of course, to participate in business not only on the direct extension of its own line, but to as many other points as possible.[99] Without some agreement, however, it would normally enjoy traffic only on the direct extension of its own line. The point Y would most naturally be reached by way of C, D or E, over the shortest routes. Competitors on either side would similarly enjoy an advantage in more direct lines from New York to the places immediately beyond them. Thus for business from New York to Z, the more direct lines through E, F or G would obviously have an advantage over lines which passed around through A, B, C or D. An almost irresistible incentive to cut-throat competition would exist. The only way the lines east of the inner circle can peaceably partition business to the outermost western points is by an agreement to make all rates between the inner and outer circles the same. In this manner the rates from A to Z or from G to X are reduced to an equality with the rates offered by the shortest route between the two rivers, which, in this case, is E Z. The rate for this shortest line then becomes the basic one, upon which all the others depend.