In the last half of the sixteenth century England emerged as a commercial and manufacturing power in Europe due to a combination of demographic, agricultural and industrial factors. The population of England and Wales grew rapidly from about 2.5 million in the 1520s to more than 3.5 million in 1580, reaching about 4.5 million in 1610. Reduced mortality rates and increased fertility, the latter probably generated by expanding work opportunities in manufacturing and farming (leading to earlier marriage and more children), explained this rapid rise in population. While epidemics and plague occasionally took their toll, the people in England still suffered less than did those in continental Europe. Furthermore, the country had been pulled out of the war that occurred in France and central Europe during the same period. England provides the prominent example of the expansion of agricultural production well before the general European agricultural revolution of the eighteenth and nineteenth centuries. A larger population stimulated the increased woollen through crop civilization. English agriculture became more efficient and market-oriented than almost anywhere else on the continent. Between 1450 and 1640 the yield of grain per acre increased by at least thirty percent. In sharp contrast with farming in Spain, English land owners brought more dense marshes and woodlands into cultivation. The great land estates of the English society largely remained intact and many wealthy land owners aggressively increased the size of their holdings, a precondition for increased productivity. Marriages between the children of landowners also increased the size of land estates. Primogeniture (the full inheritance of land by the eldest son) helped prevent land from being subdivided. Younger sons of independent land owners left the family and went to find other respective locations. Larger farms contributed more to commercialized farming at the time when an expanding population pushed up demand and prices. Farmland owners turned part of their land into pasture land for sheep in order to adapt to developing woollen trade. Some of the great land owners as well as Yeomen (farmers whose holdings and security of land tenure guaranteed their prosperity and status), organized their holdings in the interest efficiency. Many farmers selected crops for sales in growing London market. In their quest for greater profits, many land owners put their squeeze on their tenants. Between 1580 and 1620 land lords raised rents and altered conditions of land tenure in their favor, preferring shorter phases and forcing tenants to pay an entry fee before agreeing to rent them land. Landlords evicted those who could not afford annual, more onerous terms. But they also pushed tenants toward more productive farming methods, including crop rotation. England's exceptional economic development also drew the country's natural resources, including iron, timber, and coal, extracted in far greater quantity than elsewhere in the continent. New industrial development expanded the production of iron and pewter in and around the city of Birmingham. But above all textile manufacturing transformed English economy. Woolens, which accounted for eighty percent of the exports, worsteds (sturdy yarn spun from combed wool fibers), and other cloth found eager buyers in England as well as in the continent. Moreover, late in the sixteenth century as English merchants began making forays across the Atlantic these textiles were also sold in the Americas. Cloth manufacturers undercut production by urban craftspeople by "putting out" work to the villages and farms of the countryside. In such domestic industry poor rural women could spin and make cading (combing fibers in preparation for spin) in their homes. The English textile trade was closely tied to Antwerp, in the Spanish Netherlands, where workers dyed English cloth. The entrepreneur Sir Thomas Gresham became England's representative there. He so enhanced the reputation of English business in that region that English merchants could operate on credit – the most prominent achievement for sixteenth century. He also advised the government to explore the economic possibilities of Americas, which led to the first concerted efforts at colonization, undertaken with commercial profits in mind.