In 1930, total government expenditure was 10% of GDP. Of that, approximately 3% was federal spending, and 7% was state and local spending. Today, government expenditure is about 40% of GDP, with 25% of that spending federal, and the remaining 15% state and local.
Public Choice Theory provides a window into the incentives of government, providing insight into how and why bad and unpopular policies stay in place.