If you produced more consumer goods than you needed, you'd get some surplus money indicating how there was more for people to buy. If you met the demand, you would stay even. The way economics worked in HoI2, your nation had a specific demand for consumer goods and money that needed to be spent on technological research. There's a new feature that deals with government spending.
There aren't any new nations to play and all of the events in the game are the same as well (that's a bit of a disappointment). AoD just corrects a lot of bugs, adds some new features to make it more customizable, and then adds a few more to make it more realistic. The core gameplay of Arsenal of Democracy is the same as HoI2. Or to call it by it's alternate title: HoI2.5.
