RoboticGhost asks: "I wondered if you heard anything about water concerns while you were out West. I don't suspect it'd be that big of a deal in lofty Aspen, but many parts of Colorado are caught in the fight for water resources. Its town against town against farmer against industry, with some armed conflicts thrown in for good measure."

I didn't hear anything about that when I was in Colorado, but I did hear a lot about water last year when I was in Southern California and New Mexico. I'm far from an expert in this, but normally when you see shortages you're looking at an effort to allocate a valuable resource by regulatory fiat (and therefore special interest political clout) rather than price. Thus, I was strongly predisposed to favor this proposal for tradeable water rights from Michael Greenstone at Brookings when I read it months ago and reading it again it still seems right.

You can imagine some very difficult water policy questions in a desperately poor country, where people being unable to acquire a subsidence level of clean drinking water is a real issue. The United States is wealthy enough that that's not a real concern -- if people are made to pay market rates to use water, we should find that there's plenty of water around for everyone to do what we really need to do.