An exponentially increasing trend of players’ registration prices has taken place since 2012, and we test the hypothesis that this may be a speculative bubble, using a structural break test (Chow test) on a data set of international soccer players' registration prices, that ranges from 2007 to 2019. The test confirms the presence of an abrupt change in the trend of these prices since the year 2012, both for the whole data set and for subgroups based on the types of competition considered (Champions League, Europa League, and residual) and on the age of the players. We surmise that a possible root at the base of this trend is the need for soccer teams to cope with the Fair Play regulation, which has taken place exactly in the same years, and caused an excess of players’ trading as a means to comply with the obligation for teams to balance their books over time.

中文翻译：

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足球泡沫：国际足球运动员的身价是否存在投机泡沫？

自2012年以来，球员注册价格出现了指数级增长的趋势，我们对国际足球运动员注册价格数据集使用结构性突破测试（Chow测试）来检验这可能是投机泡沫的假设，即范围从 2007 年到 2019 年。测试证实，自 2012 年以来，这些价格的趋势存在突然变化，无论是对于整个数据集还是基于所考虑的比赛类型的子组（欧洲冠军联赛、欧洲联赛和剩余）和球员的年龄。我们推测，这一趋势的根源可能是足球队需要应对公平竞赛规则，该规则恰好在同一年实施，并导致球员交易过多，以此作为遵守公平竞赛规则的手段。团队有义务随着时间的推移平衡他们的账目。