http://en.wikipedia.org/wiki/The_Black_Death#Socio-economic_effectsSocio-economic effects
Monks, disfigured by the plague, being blessed by a priest. England, 1360–75.The governments of Europe had no apparent response to the crisis because no one knew its cause or how it spread. Most monarchs instituted measures that prohibited exports of foodstuffs, condemned black market speculators, set price controls on grain, and outlawed large-scale fishing. At best, they proved mostly unenforceable, and at worst they contributed to a continent-wide downward spiral. The hardest hit lands, like England, were unable to buy grain abroad: from France because of the prohibition, and from most of the rest of the grain producers because of crop failures from shortage of labour. Any grain that could be shipped was eventually taken by pirates or looters to be sold on the black market. Meanwhile, many of the largest countries, most notably England and Scotland, had been at war, using up much of their treasury and exacerbating inflation. In 1337, on the eve of the first wave of the Black Death, England and France went to war in what would become known as the Hundred Years' War, further depleting their treasuries, population, and infrastructure. Malnutrition, poverty, disease and hunger, coupled with war, growing inflation and other economic concerns made Europe in the mid-fourteenth century ripe for tragedy.
The plague did more than just devastate the medieval population; it caused a substantial change in economy and society in all areas of the world. Economic historians like Fernand Braudel have concluded that Black Death exacerbated a recession in the European economy that had been under way since the beginning of the century. As a consequence, social and economic change greatly accelerated during the fourteenth and fifteenth centuries. The church's power was weakened, and in some cases, the social roles it had played were replaced by secular ones. Also the plague led to peasant uprisings in many parts of Europe, such as France (the Jacquerie rebellion), Italy (the Ciompi rebellion, which swept the city of Florence), and in England (the English Peasant Revolt).
Europe had been overpopulated before the plague, and a reduction of 30% to 50% of the population could have resulted in higher wages and more available land and food for peasants because of less competition for resources. However, for reasons that are still debated, population levels in fact continued to decline until around 1420 and did not begin to rise again until 1470, so the initial Black Death event on its own does not entirely provide a satisfactory explanation to this extended period of decline in prosperity. See Medieval demography for a more complete treatment of this issue and current theories on why improvements in living standards took longer to evolve.
The great population loss brought economic changes based on increased social mobility, as depopulation further eroded the peasants' already weakened obligations to remain on their traditional holdings. In Western Europe, the sudden scarcity of cheap labour provided an incentive for landlords to compete for peasants with wages and freedoms, an innovation that, some argue, represents the roots of capitalism, and the resulting social upheaval caused the Renaissance and even Reformation. In many ways the Black Death improved the situation of surviving peasants. In Western Europe, because of the shortage of labour they were in more demand and had more power, and because of the reduced population, there was more fertile land available; however, the benefits would not be fully realized until 1470, nearly 120 years later, when overall population levels finally began to rise again.
Social mobility as result of the Black Death has been postulated as most likely cause of the Great Vowel Shift, which is the principal reason why the spelling system in English today no longer reflects its pronunciation.
In Eastern Europe, by contrast, renewed stringency of laws tied the remaining peasant population more tightly to the land than ever before through serfdom. Sparsely populated Eastern Europe was less affected by the Black Death and so peasant revolts were less common in the fourteenth and fifteenth centuries, not occurring in the east until the sixteenth through nineteenth centuries. Since it is believed to have in part caused the social upheavals of fourteenth- and fifteenth-century Western Europe, some see the Black Death as a factor in the Renaissance and even the Reformation in Western Europe. Therefore, historians have cited the smaller impact of the plague as a contributing factor in Eastern Europe's failure to experience either of these movements on a similar scale. Extrapolating from this, the Black Death may be seen as partly responsible for Eastern Europe's considerable lag in scientific and philosophical advances as well as in the move to liberalise government by restricting the power of the monarch and aristocracy. A common example is that England is seen to have effectively ended serfdom by 1550 while moving towards more representative government; meanwhile, Russia did not abolish serfdom until an autocratic tsar decreed so in 1861.
On top of all this, the plague's great population reduction brought cheaper land prices, more food for the average peasant, and a relatively large increase in per capita income among the peasantry, if not immediately, in the coming century. Since the plague left vast areas of farmland untended, they were made available for pasture and put more meat on the market; the consumption of meat and dairy products went up, as did the export of beef and butter from the Low Countries, Scandinavia and northern Germany. However, the upper class often attempted to stop these changes, initially in Western Europe, and more forcefully and successfully in Eastern Europe, by instituting sumptuary laws. These regulated what people (particularly of the peasant class) could wear, so that nobles could ensure that peasants did not begin to dress and act as a higher class member with their increased wealth. Another tactic was to fix prices and wages so that peasants could not demand more with increasing value. This was met with varying success depending on the amount of rebellion it inspired; such a law was one of the causes of the 1381 Peasants' Revolt in England.
http://en.wikipedia.org/wiki/The_Black_Death#Socio-economic_effects