turned to Christianity as a spiritual tool to build one. By 1900, there were about 1,400 Catholic priests and nuns in China serving nearly 1 million Catholics. Over 3,000 Protestant missionaries were active among the 250,000 Protestant Christians in China. Western medical missionaries established clinics and hospitals, and led medical training in China. Missionaries began establishing nurse training schools in the late 1880s, but nursing of sick men by women was rejected by local tradition, so the number of students was small until the 1930s. Economy By the end of the 17th century, the Chinese economy had recovered from the devastation caused by the wars in which the Ming dynasty were overthrown, and the resulting breakdown of order. In the following century, markets continued to expand as in the late Ming period, but with more trade between regions, a greater dependence on overseas markets and a greatly increased population. By the end of the 18th century the population had risen to 300 million from approximately 150 million during the late Ming dynasty. The dramatic rise in population was due to several reasons, including the long period of peace and stability in the 18th century and the import of new crops China received from the Americas, including peanuts, sweet potatoes and maize. New species of rice from Southeast Asia led to a huge increase in production. Merchant guilds proliferated in all of the growing Chinese cities and often acquired great social and even political influence. Rich merchants with official connections built up huge fortunes and patronized literature, theater and the arts. Textile and handicraft production boomed. The government broadened land ownership by returning land that had been sold to large landowners in the late Ming period by families unable to pay the land tax. To give people more incentives to participate in the market, they reduced the tax burden in comparison with the late Ming, and replaced the corvée system with a head tax used to hire laborers. The administration of the Grand Canal was made more efficient, and transport opened to private merchants. A system of monitoring grain prices eliminated severe shortages, and enabled the price of rice to rise slowly and smoothly through the 18th century. Wary of the power of wealthy merchants, Qing rulers limited their trading licenses and usually refused them permission to open new mines, except in poor areas. These restrictions on domestic resource exploration, as