On the night of Oct. 3, 1990, German dignitaries sang the national anthem on the balcony of the Reichstag in Berlin. In the surrounding streets, people celebrated with German flags and bottles of sparkling wine. It was the night that marked the completion of German reunification – and, many believed, the end of the migration of East Germans to the West. Hardly anyone suspected that many regions in the East would soon face a new wave of emigration and a severe demographic crisis.

ZEIT ONLINE has evaluated data on each of the approximately 6 million moves from eastern Germany to western Germany that took place from 1991, the first full year German unification, to 2017. The data tells one of the least documented stories of German post-war history, showing that after reunification, nearly a quarter of the original population of East Germany moved to the West. In all, 3,681,649 people left. The data also shows that the 2,451,176 moves from the West to the East weren’t enough to stop the decline in many places. For the first time, we now have a clear view of what exactly happened in every region of the East and West after the fall of the Berlin Wall.

Shortly after the collapse of communism, the pollsters at Emnid surveyed former East Germans about their lives. These polls registered a level of depression among East Germans that had “never been seen before, not anywhere.” More than a third of the adult population had the feeling that they were “no longer needed in society.” The sociologist Paul Windolf estimates that in the five years after the Berlin Wall fell, up to 80 percent of working East Germans lost their jobs either temporarily or permanently. There were, to be sure, a handful of success stories in the East even then, but in many places, poverty, fear and resignation set in.

The severity of emigration’s impact on the East is most apparent when one takes a closer look at the administrative districts and cities in the region. Nearly every district lost people to the West between 1991 and 2017. Not only did states in eastern Germany lose tax revenues as a result, but in many places the “social infrastructure” also collapsed; schools, hospitals, sports and leisure facilities and cultural institutions all had to close.

It has taken nearly 30 years, but half of all eastern German regions finally have a positive migration balance with western German states. For the first time, more people are moving from West to East than the other way around. That is primarily due to the fact that fewer and fewer people are leaving the East – in part because there are hardly any people left in many regions who are both willing to migrate and able to do so. But it is also because many large cities and regions in the former East have become a draw, places like Potsdam or Leipzig, for example.

Where did the millions of people go who left the East over the years? A look at the map at the beginning of this article shows a heavy stream leaving the state of Saxony for southern Germany. They went to places like Erding and Freising in the state of Bavaria, for instance, not far from where Munich’s new airport opened in 1992, sparking an economic upswing that created thousands of jobs in the subsequent decade.

Other winners included mid-sized cities in the state of Baden-Württemberg like Heilbronn and Pforzheim. But if you only look at the absolute number of arrivals, one city stands out: Hamburg. No other western German city absorbed more people from eastern Germany: In all, some 190,000 people from the East made their way to the northern German port city. Most of them came from the nearby state of Mecklenburg-Western Pomerania.

Migration to the West wasn’t the only thing that altered the demography of eastern Germany. The social upheavals that followed reunification caused the birth rate in the East to plunge. From 1990 to 1994, the birth rate dropped by nearly half. Many women and men who weren’t sure whether they were going to lose their job either put off starting a family or gave up their plans altogether. Nowadays, the number of children born in the East is slightly higher than in the West. But the gap that arose in the 1990s is far from closed, and many places are aging.

The consequences of this shift are on full display in the small town of Suhl. No other region has lost as many people since 1991 as this former district capital in the state of Thuringia. Prior to reunification, Suhl flourished thanks to the vehicle and weapons manufacturer Ernst Thälmann, which also produced Simson motorcycles. But after the fall of the Wall, the company was privatized and the Simson brand was no longer produced. More than a third of the town’s residents left. All in all, Suhl lost about 15 percent of its residents to the West and 24 percent to other eastern German regions. Furthermore, far more people died than were born.

Recently, however, the city has been attracting more people from western German states. And something else stands out in our graphic, as well: Foreigners in particular moved to Suhl. One reason for this is that since 2014, the city has played host to a central reception facility for asylum seekers. Immigrants could, in fact, serve to stabilize demographics not only in Suhl, but in other places in the East as well. But there’s a catch: Areas that have experienced the greatest population loss are more susceptible to right-wing populist parties.

Since reunification, more than a quarter of the eastern German population between the ages of 18 and 30 migrated to the West. One could see this as a necessary adjustment process of the kind that takes place in dynamic economies: a zero-sum game in which western German regions benefitted from the fact that eastern German regions were struggling.

Yet people live in social and political contexts, and these are difficult to shift. Decades of emigration have had adverse effects on the East that will not be so quick to disappear. Even in Germany’s past boom years, progress in the East was sluggish. A lack of social and technical infrastructure, such as schools, libraries and public transportation, kept people away from many regions and prevented a sustainable recovery. The result has been a sense of frustration that has long been manifested politically.

These days, some western German regions are suffering from a loss of residents as well. And in the East, there are cities that have become crowded. Leipzig, for instance, is the fastest growing city in Germany today. Even the flow of migration between Bavaria and Saxony has reversed: Today, more people from the southern German state are moving to its formerly East German neighbor than the other way around.

In many of the East’s depleted regions, however, nothing has changed. Hardly any new young people are moving there and the population just gets older and older. All it takes is one look at the map depicting age composition to see that eastern Germany today resembles an ever-darkening patchwork with just a few lighter spots.

Why should that concern the West? For some western German regions, a look at the aging regions in the former East could provide a view of their own future. In the West, too, the gap is growing between areas of urban sprawl and their peripheries, between areas that are up-and-coming and those that are dying. The difference between East and West is narrowing – at least demographically.