"After the Berlin Wall came down, millions of East Germans who stayed behind decided against producing another generation. Their fertility more than halved. In 1988, 216,000 babies were born in East Germany; in 1994, just 88,000 were born. The fertility rate worked out at 0.8 children per woman. Since then it has struggled up to around 1.2, but that is still only just over half the rate needed to maintain the population. About a million homes have been abandoned, and the government is demolishing them as fast as it can. Left behind are "perforated cities", with huge random chunks of wasteland. Europe hasn't seen cityscapes like this since the bombing of the second world war.
And nowhere has emptied as much as Hoyerswerda. In the 80s, it had a population of 75,000 and the highest birth rate in East Germany. Today, the town's population has halved."
The problem seems to be a combination of women leaving town and a generational disinclination to have children.