This added to uncertainty, and the interruptions coincide with dramatic drops in renewables investment in the US (see drops in installed capacity in 2000, 2002, and 2004 in Figure 23, for an elaborate study of the case see Barradale 2008). Thus, to make use of this privilieged tax regime, RE developers have to cooperate/merge w'ith large established companies, which provide the tax liability against which the PTC can be claimed. During the last decade three major policies have been implemented which we consider to support directly investment in physical capital.