@urlyman @svavar

It is a very clear example of how decisions governments made decades ago can still affect people today. There's a lot of good info on Germany specifically here: https://en.wikipedia.org/wiki/New_states_of_Germany

Interestingly, we have the same thing in Poland, the so called "Poland A and Poland B": https://en.wikipedia.org/wiki/Poland_A_and_B which goes back to the times when Poland was partitioned. The Prussian parts were much better developed compared to the Austrian and Russian ones which stayed mostly agrarian.