Calls himself an economist and does not get the reference. OK, let me spell it out. Maybe it'll be useful to others. Before Krugman and Helpman, the theory of comparative advantage predicted that countries should specialize in different products. But the reality was that, within the transatlantic core of the world economy, countries were making the same thing like cars and tvs. Krugman and Helpmen resolved this puzzle by showing how product differentiation meant that countries could make similar products and still conduct a massive amount of trade. China is now making similar things as the AEs because China has successfully climbed the ladder. This is exactly what modern trade theory would lead you to expect.