The data, released ahead of the 25th anniversary of German reunification on Saturday, showed that the population of the five states that once formed East Germany had fallen from some 14.5 million in 1991 to 12.5 million in 2013.
Those living in the eastern states now represent some 15 percent of the German population, down 3 percent from the 18 percent at the time of reunification.
While 3.3 million easterners moved west, only 2.1 million west Germans moved to the former east during that time.
A graying population
Many of those who have left appear to have been young people, with the proportion of the population in the east aged more than 65 having jumped from some 10 percent in 1991 to 24 percent in 2013. That compares with a figure of 20 percent for the West.
"The reasons for the loss of some 2 million people are high migration away from the new states, and a birth rate deficit," said Destatis President Roderich Egeler, presenting the findings.
"The fall of the Berlin Wall sparked a strong movement of migration away," he added.
However, the trend does appear to now be reversing, with 2013 being the first year that more people moved from western Germany to Berlin and the eastern states than in the other direction.
Fewer economic opportunities
The study found that industry in the East German states remains far weaker than the rest of the country.
According to the figures, unemployment figures in the former East German states have improved - down from 17.7 percent to just under 12 percent.
Even so, that figure remains far higher than for the western states, where unemployment stands at 6.2 percent - with 2.9 million people officially out of work.
Manufacturing in the former east contributed 3.7 per cent to the unified German economy in 1991, Destatis said, with the dismantling of the communist economy leading many factories to close their doors.
More than two decades later, in 2013, the contribution to industry from the former east had recovered and climbed to 8.7 per cent of Germany's total output, still relatively low on a per capita bases. The pace at which eastern states were catching up appeared to have been reversed by the global financial crisis in 2008, Destatis said. In 2008, eastern Germany's share had stood at 9.8 percent.
rc/kms (AFP, dpa)