 With the closing of the Inner German border officially in 1952, the Berlin city sector borders remained considerably more accessible than the rest of the border because of their administration by all four occupying powers.Accordingly, it effectively comprised a "loophole" through which Eastern Bloc citizens could still move west.The 3.5 million East Germans that had left by 1961, called Republikflucht, totaled approximately 20% of the entire East German population.