Trade liberalization may shift economic inequality from a global to a domestic scale. When rich countries trade with poor countries, the low-skilled workers in the rich countries may see reduced wages as a result of the competition, while low-skilled workers in the poor countries may see increased wages. Trade economist Paul Krugman estimates that trade liberalisation has had a measurable effect on the rising inequality in the United States. He attributes this trend to increased trade with poor countries and the fragmentation of the means of production, resulting in low skilled jobs becoming more tradeable. However, he concedes that the effect of trade on inequality in America is minor when compared to other causes, such as technological innovation, a view shared by other experts. Empirical economists Max Roser and Jesus Crespo-Cuaresma find support in the data that international trade is increasing income inequality. They empirically confirm the predictions of the Stolper–Samuelson theorem regarding the effects of international trade on the distribution of incomes. Lawrence Katz estimates that trade has only accounted for 5-15% of rising income inequality. Robert Lawrence argues that technological innovation and automation has meant that low-skilled jobs have been replaced by machine labor in wealthier nations, and that wealthier countries no longer have significant numbers of low-skilled manufacturing workers that could be affected by competition from poor countries.