In many nations around the world, corruption is a serious problem. It is regarded as a weapon of mass destruction that has greatly damaged several nations' public and private sectors.
Several of the factors that contribute to corruption are listed below:
(1) Government size and structure
Government size isn't inherently terrible as long as the government doesn't interfere with basic liberties and participants in the government don't use the office for personal gain. Of course, that's logic that would exist in a vacuum which doesn't account for real world factors. I'm generally for limited government and small government size because it reduces the tendency for a central authority to begin housing the authority for corruption.
(4) Economic freedom/openness
Most important on your list IMO. Authoritarianism/corruption is always about the money. Decentralized currencies would of course help with this issue.