The Murray-Darling Basin is Australia’s largest river system spanning over a million square kilometres and supporting annual agricultural production in excess of $A24 billion. The market for trading in water entitlements linked to this resource seeks to ensure that water flows to its highest value use. The quality of the data produced for these markets is of paramount importance to all participants, whether it be irrigators assessing whether the price offered for their entitlement is fair or a water authority attempting to determine the impact of their intervention through buyback activity. In this paper, we highlight the problem of using median prices when reporting aggregate price levels. We demonstrate that a median-based price index reflects changes in the composition of entitlement sales each month in addition to any general change in aggregate prices. We employ the repeat-sales technique, historically used to construct house price indices, in the novel setting of water entitlement trading to overcome this distortion.

JEL Classification: Q25, G10

Murray-Darling盆地是澳大利亚最大的河流系统，面积超过100万平方公里，支持的年度农业产量超过240亿澳元。与该资源有关的水权交易市场力求确保水流向其最高价值使用。这些市场所产生的数据质量对于所有参与者而言都是至关重要的，无论是灌溉商评估其应得的价格是否公平，还是水务部门试图通过回购活动来确定其干预的影响。在本文中，我们重点介绍了在报告总价格水平时使用中位数价格的问题。我们证明，基于中位数的价格指数除了反映了总价格的任何一般变化之外，还反映了每月权利销售构成的变化。我们在水权交易的新颖环境中采用了历史上用来构建房价指数的重复销售技术来克服这种扭曲。

JEL分类：Q25，G10