Let's dive a bit deeper. In fact this report has a graph stating the 61% decline in Wind energy prices from 2009 to 2015:
Figure 1: Unsubsidized Levelized Cost of Energy Wind (Historical)
But what happened before 2009? The DoE has published a much larger report that has a longer timescale (DoE 2014 Wind Technologies market report). The report page 57:
Figure 2: Generation-weighted average levelized wind PPA
prices by PPA execution date and region (DoE)
So from 2003 to 2009 the prices increased and then fell back from 2009 to 2014. Perhaps the increase was due to a subsidy system? And perhaps now the wind energy industry would like to get another generous subsidy system because it is hard to compete with falling oil prices (Nasdaq: Brent price)?
So they get Paul Krugman to cherry pick time scales.
Link to this news: http://bit.ly/1Kn3hnr