Entry and Exit in Hub-Spoke Networks
解释为何区域承运人在枢纽辐射网络中难以生存：当区域承运人与枢纽运营商在支线市场竞争时，双方均亏损；但枢纽运营商若退出支线市场，其连接市场的利润会下降。若连接市场足够多，枢纽运营商不退出支线市场是占优策略，区域承运人则因固定成本非沉没而被迫退出。
We offer an explanation for why regional carriers may not survive in hub-spoke networks.When a regional carrier and a hub operator compete in a spoke market, both will suffer losses in that market.But if the hub operator exits in the spoke market, its profits in connecting markets will fall.As long as the number of such markets is large enough, it is a dominant strategy for the hub operator not to exit from the spoke market.The regional carrier is then forced to exit, assuming fixed costs are not sunk.