During this time period, the population of Europe rose and then fell again. By the end of the period, it was beginning again to rise slowly.
At the start of this period, the population of Europe was rising rapidly. This was due largely to improvements in farm technology. These improvements allowed farmers to grow more and thereby feed more people. By 1300, Europe's population was estimated at 100 million people.
But then the 14th century was a time of horrible decline. This was a time in which Europe was hit by famine caused by the "little ice age." It was the century in which the Black Death killed so many Europeans. It was also a century torn by war. All of these things combined to make the population drop severly. The population of Europe is believed to have dropped by anywhere from 25 to 50%. The population would not get back to 13th century levels until after 1500.