However, responding to the work of Bairoch, Pomeranz, Parthasarathi and others more subsequent research have found that parts of 18th century Western Europe did have higher wages and levels of per capita income than in much of India, Ottoman Turkey, Japan and China. However, the views of Adam Smith were found to have overgeneralized Chinese poverty. Between 1725 and 1825 laborers in Beijing and Delhi were only able to purchase a basket of goods at a subsistence level, while laborers in London and Amsterdam were able to purchase goods at between 4 and 6 times a subsistence level. As early as 1600 Indian GDP per capita was about 60% the British level. A real decline in per capita income did occur in both China and India but in India began during the Mughal period before British colonialism. Outside of Europe much of this decline and stagnation has been attributed to population growth in rural areas outstripping growth in cultivated land as well as internal political turmoil. Free colonials in British North America were considered by historians and economists in a survey of academics to be amongst the most well off people in the world on the eve of the American Revolution. The earliest evidence of a major health transition leading to increased life expectancy began in Europe in the 1770s, approximately one century before Asia's. Robert Allen argues that the relatively high wages in eighteenth century Britain both encouraged the adoption of labour-saving technology and worker training and education, leading to industrialisation.