My student Jason Hwang successfully defended his dissertation this morning. Probably the most important and interesting of his findings is that countries converge to the global productivity frontier in individual products unconditionally. A country that exports, say, color TVs, will eventually and as a matter of course catch up with unit values of the richest countries that produce the same good, and will do so at a relatively rapid rate of 5% per year. This is to be contrasted with convergence at the economy-level, which happens only conditionally--i.e., after a long list of prerequisites are satisfied--and much more slowly. Rapidly growing countries are those that are, counterintuitively, farther away from the productivity frontier of the goods that they export. Diversification of production acts like a convergence machine: it enables countries to get into the lower rungs of taller ladders. This is fascinating stuff, and opens up really new ways of looking at the links between structural change and economic convergence.