Concentrate Development can lead to ridiculous amounts of development in the capital, and I don't like it. Disabling it altogether is not a good solution, because I like this feature, and I think it's very useful in preventing your subjects from growing too fast, which increases their liberty desire. So it's better to steal some development from them, and get some temporary LD, but in the long run it reduces the LD of all the subjects.

I tried to fix it by reducing the amount of development that goes to the capital from 50% to 5% in the defines, but there is another problem: all the amount that doesn't go to the capital goes to one specific province. For example, I'm playing as France and Catalonia is my vassal, with two states. Whenever I concentrate development in one of the states, all the non-capital amount goes to the province of Aix. So instead of ridiculous amounts of development in Paris, I have it in Aix. Probably it's a base game problem, but if anyone has any idea how to fix it in ET, please let me know.