The rationale for continued cost declines that I encounter most often is based on volume: If we install more wind and solar capacity, costs will fall in a virtuous cycle, making subsequent installations cheaper and prompting even more of them. The underlying logic behind this argument derives from empirically observed "experience curves", in which cost components such as manufacturing fall by a set percentage for each doubling of cumulative output. The problem with these curves is that they tend to flatten out fairly quickly, delivering their maximum effect in the early years of a technology, when doublings are frequent.