The Qing conquest theory proposes that the actions and policies of the Manchu-led Qing dynasty held China back, and led to the Great Divergence in which China lost its early modern economic and industrial lead over the West. The theory seeks to explain why Europe could experience an industrial revolution, but China did not. Theory supporters, some of whom may be motivated by anti-Qing sentiment, claim that advances in science and technology and economic development in the Song and Ming dynasties moved China toward a modern age, however, the restrictions placed on commerce and industry and the persecution of non-orthodox thought after the transition from Ming to Qing in the 17th century caused China to gradually stagnate and fall behind the West. Background Different dates are offered for the beginning or end of ascendency and whether it was in economic, technological, or political terms. Some see the Qing as the time when China fell behind, either because of stagnation or because Europe or the West pulled ahead. The economic historian Angus Maddison calculates that in the tenth century China was the "world's leading economy in terms of per capita income," and that "between the fifteenth and eighteenth centuries economic leadership passed from China to Western Europe." Carl Dahlman and Jean-Eric Aubert of the World Bank argue, based on Maddison's data, that China was the world's largest and most advanced economy for the most of the past two millennia and among the wealthiest and most advanced economies until the 18th century. Maddison believes that China's lead did not happen until the fall of the Roman Empire and that China lost its lead because Europe pulled ahead, not because of domestic conditions. In a review of the field in 2006, the Harvard economic historian David Landes began by stating that "as late as the end of the first millenium of our era, the civilizations of Asia were well ahead of Europe in wealth and knowledge," but five hundred years, that is, in the early years of the Ming dynasty, later "the tables had turned." The economic historian Mark Elvin, drawing on the work of Japanese historians, argues that the Song dynasty (960–1279), experienced a revolution in agriculture, water transport, finance, urbanization, science and technology, but that China was then caught in a high level equilibrium trap. Others claim that the Song dynasty economic revolution brought proto-industrialization with large increases in per capita