Last week I talked about the water problem and how water is unique among economically productive commodities. Most commodities are substitutable – that is, you can use something else in place of the commodity, if you really need to. Few commodities have perfect substitutes; corn is not exactly the same thing as wheat, barley is not a perfect substitute for rye. But if the wheat crop fails, we don’t all starve; we substitute other grain products for wheat and get by. Water, of course, is different….to read more visit http://blog.alextiller.com