地铁企业普遍存在着行业性的政策性亏损。其实,地铁企业亏损的根本原因并非是由于产出少,而是因为地铁项目具有巨大的正外部性。正外部性是指某一市场主体的活动给别的主体带来了可以无偿得到的收益。地铁项目的建设与运营,至少有以下四大类直接产出:地铁设施、附属资源、沿线 Subway companies widespread industry-wide policy losses. In fact, the root cause of the loss of the MTRC is not due to less output but because of the huge positive externalities of the MTRC. Positive externalities mean that the activities of a certain market body bring benefits to other subjects for free. Subway project construction and operation, at least the following four categories of direct output: subway facilities, ancillary resources, along