Patent transactions were quite active in 2011 and 2012 with unprecedented high values. However, the patent market showed an evident decline since 2013, with both the number and price of traded patents dropping signiifcantly. By summarizing both patent trade-related statistics from various professional agencies and valuing methods used therein, causes of the above mentioned trends along patent transactions can be explored, and leads to the speculative conclusion that the United States, being the center of the global patent market for many years, has undergone a series of recent developments concerning patent legislation, judicial rulings and industrial policies, all of which might have deeply affected the patent market in a negative way.%专利交易在2011年—2012年非常活跃，专利估值也高，不过在2013年之后却有明显下降。通过总结相关专业机构对专利交易的数据统计以及专利交易中的估值方法，探究专利交易趋势变化背后存在的原因，可以得出结论：美国作为全球专利交易的中心，其立法、司法和政策环境都发生了一些变化，并影响了全球专利交易的走势。
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