How was the Wester European economy accelerated by the changes (the availability and price of labor, the end of the feudal system and inovation of new technology) that the Black Death brought?
Any time there is a sudden and massive decrease in available manpower, the survivors will find themselves required to step up their productivity and ingenuity. I have wondered what will happen if society breaks down and my car needs service; I don't know how to work on cars, and the people who do will be in high demand.
During the Black Plague, the poor were the greatest victims, since they had low standards of hygiene and little access to medicine. Since in a feudal system the poor are also the people doing all the menial labor and farming, this meant that the surviving elites needed to learn how to farm and produce before winter set in. Necessity is, after all, the mother of invention; here, desperation played a large role as well.
It is important to remember that the Black Death was not the only dire event that struck Europe, setting many of the trends mentioned in this thread in motion. In particular, Europe, especially northern Europe, endured one of the worst famines in its history, as well as the enormously destructive Hundred Years War.
My understanding is that many things affected the economy in Europe at this time. There were several reasons for the decline of the feudal system: including the invention of the long bow which could piece a knight's armor from a distance; another enormous change was the ability of poor serfs to raise sheep. The cost of wool imported from the Continent was high...in England, poor people stopped working for feudal lords and began raising sheep. English wool was soon preferred. Castles became obsolete.
The Black Death (plague) killed so many people that work would have been easier to find with a reduction in population.
The plague (and any disease) kills the old and weak more quickly, but the Black Death knew no boundaries: kings were as susceptible as peasants because they had no way of knowing how to stop the spread of the disease. Pohnpei397 hits it on the head: when there were many people looking for jobs, merchants, etc., could afford to pay lower wages. With the shortage of workers, wages had to be competitive—higher. Anytime a business wants to make a profit, it has to find ways to decrease costs. Technological advances would have helped, even if they were archaic compared to what we would see developed during the Industrial Revolution hundreds of years later.
I have to agree that The Black Death plagued the ill and old. That being said, the vast amounts of deaths did impact Europe. Europeans needed to find ways to curtail the shortages in man-power and experience. Europe did, in fact, become stronger because of the problems associated with the disease.
The Black Death prayed mostly on the weak. It was survival of the fittest, so while many people died, those who survived were the strongest ones. So you could argue that The Black Death eventually made Europe and the people stronger.
Black Death brought with it massive changes in society that had far-reaching ramifications. This was mostly created by the shortage of bodies who could carry out labour, suddenly giving the farm hands power that they had never had before. They were able to negotatiate a wage to suit them that effectively ended the social structure of the time.
All three factors enhanced productivity and competition. I read recently that most of the people who died during the Black Death were the old and the infirm. In crude Darwinistic terms, this meant that those who survived tended to be the young and the strong.
With all of these influences, Europe became a more productive place. Because labor was more expensive, it was necessary to figure out ways to produce that would use less labor. Because of the end of the feudal system, there was more incentive to make money because a rich person could move up in society where he (in those days) could not have under feudalism. These things caused there to be more incentive to innovate. More innovation made the economy more productive.
You've succinctly stated the case -- the Black Death caused a shortage of labor, which brought about less labor intensive agricultural techniques. Labor was scarce, and in demand, and was therefore expensive, so farm hands could strike their own deal. That single point finally did in feudalism in Western Europe -- no longer were laborers tied to the soil. Agriculture became efficient; excess farm laborers became craftsmen and the era of guilds began. These fundamental economic shifts caused by the Black Death ended the Medieval period and laid the groundwork for the Renaissance a few decades later.