Europe and the United States, WTO accession did not lead to lower trade barriers. However, China's MFN status had been subject to annual approval by Congress in the United States; research has suggested that this caused uncertainty, and discouraged China-U.S. trade. Political impact Studies have linked the effects of the China shock to an increase in populism and a backlash against globalization. Studies have shown that British regions that were more exposed to Chinese import competition were more likely to vote for Brexit in the 2016 referendum. Exposure to the China shock has led to negative views of minorities, in particular among American whites and males. Papers have found that the China shock has contributed to political polarization. One analysis also found that it contributed to Donald Trump's victory in the 2016 presidential election: "A counterfactual study of closely contested states suggests that Michigan, Wisconsin, and Pennsylvania would have elected the Democrat instead of the Republican candidate if, ceteris paribus, the growth in Chinese import penetration had been 50 percent lower than the actual growth during the period of analysis. The Democrat candidate would also have obtained a majority in the electoral college in this counterfactual scenario." In Italy, surges in support for the Lega Nord in the 2010s have been observed in localities where textile mills were undercut by Chinese manufacturers. Social impact A 2016 study found that exposure to Chinese import competition led to greater high school graduation rates in the United States. This is possibly because of lower wages and employment opportunities for individuals without high school degrees in regions that competed with China. Economist Samuel Hammond, the director of poverty and welfare policy for the Niskanen Center, has argued that the signing into law of Permanent Normal Trade Relations (PNTR) with China on October 10, 2000 and the subsequent accession of China to the WTO has had wide reaching social implications. He states that the "PNTR has been implicated in some of the most significant and distressing trends of American life in this century: millions of well-paying manufacturing jobs lost; declining family formation and rising deaths of despair; soaring real-estate prices and medieval levels of urban inequality; increased political polarization and populist movements, left and right; and faltering faith in the power of liberal democracy to respond to these and related challenges. To pin all this on a single trade agreement would be a step too