China's wind power capacity has increased dramatically in recent years, but about 30% of the installed capacity sits idle, so overinvestment in wind power capacity seems to be a serious problem. This paper explores reasons for the overinvestment. The economic analysis shows that, given uncertain future policy on wind power, it is optimal for power companies to invest more than the amount in a certain world. A part of the "overinvestment" has a real value, which can be interpreted as the value of holding scarce wind resource. This value exists because the wind-rich sites with convenient locations to connect to the grids are scarce resource, and also because the specific government policies that are essential for promoting wind power are uncertain in the future. This value should be taken into account in the investment decision, but it results in the phenomenon of "overinvestment". The concept of the value of holding scarce resource can be generally applied to the resources that are scarce and for which the future policy is uncertain. (c) 2013 Elsevier Ltd. All rights reserved.