The job creation claims rest on two obvious premises: the viability of wind energy and economic efficiency of government investments in it. The first point is hotly disputed. Wind energy is expensive and intermittent. Conventional energy sources can be ramped up or down in a few hours; when the wind blows is an entirely different question. The industry is supported by a federal production tax credit. As Competitive Enterprise Institute energy policy analyst William Yeatman pointed out in an interview, wind advocates warned last December that the industry would lose thousands of jobs practically overnight if Congress did not renew the Federal subsidy.