By the end of the eighties the brotherhoods began to press energetically for improvements in employment conditions and found the railways not disinclined to grant their demands in a measure. This was due in great measure to the strategic position of these trades, which have it in their power completely to tie up the industry when on strike, causing enormous losses to the carriers.[60] Accordingly, they were granted wages which fairly placed them among the lower professional groups in society as well as other privileges, notably "seniority" in promotion, that is promotion based on length of service and not on a free selection by the officials. Seniority was all the more important since the train personnel service is so organized that each employe will pass several times in the regular course of his career from a lower to a higher rung on the industrial ladder.[61] For instance, a typical passenger train engineer starts as fireman on a freight train, advances to a fireman on a passenger train, then to engineer on a freight train, and finally to engineer on a passenger train. A similar sequence is arranged in advancing from brakeman to conductor. Along with seniority the brotherhoods received the right of appeal in cases of discharge, which has done much to eliminate discrimination. Since they were enjoying such exceptional advantages relative to income, to the security of the job, and to the stability of their organization, it is not surprising, in view of the limited class solidarity among American laboring men in general, that these groups of workers should have chosen to stand alone in their wage bargaining and that their refusal to enter "entangling alliances" with other less favored groups should have gone even to the length of staying out of the American Federation of Labor. This condition of relative harmony between employer and employe, notwithstanding the energetic bargaining, continued for about fifteen years until it was disturbed by factors beyond the control of either railway companies or brotherhoods. The steady rise in the cost of living forced the brotherhoods to intensify their demands for increased wages. At the same time an ever tightening regulation of railway rates by the Federal government since 1906 practically prevented a shift of increased costs to the shipper. "Class struggles" on the railways began in earnest. The new situation was brought home to the brotherhoods in the course of several wage arbitration cases in which they figured.[62] The outcome taught them that the public will give them only limited support in their efforts to maintain their real income at the old high level compared with other classes of workers.