Difficult to understate the importance of this blog post

Macher and Richman’s review of empirical research on transaction cost economics (working paper version, published in Business and Politics earlier this year) includes this statement about the importance of TCE research relating to economic development:

It is perhaps difficult to understate the policy implications of this research, especially as developing countries consider implementing a host of new and unproven approaches.

Let me try to understate its importance: “It’s not important at all.” See, that wasn’t so difficult.

“Difficult to understate” gets 750 google hits, some of which seem like appropriate uses but many of which seem to reflect the same mistake Macher and Richman made. (By contrast, “difficult to overstate” gets 96,100.)