@cockswain I can’t give you a percentage, but a huge chunk of big bank funds is in their profits from the various loans they give. If you take your money out and limit their ability, you definitely effect one of their big income sources, which frankly they have been taking advantage of in recent years (see the mortgage crisis that prompted our current economic downturn and destroyed several huge banks).
Credit Unions can make the same risky investments that big banks do, but by in large they do not because they are not for profit. They make enough money to pay their staff, build some reserves, but the rest of the “profit” is passed onto the members. They are not immune to corruption but tend to avoid it better than large banks. As such, CU’s are a lot more likely (again I don’t know the percentage, but I have seen the studies/reports) to loan money than a major bank. They also tend to give better rates.
The thought behind putting money in the CU’s is that the big banks would have to take notice and begin to amend their policies to compete with the CU’s. Unfortunately though, one of the huge side effects of being a non-profit entity such as a CU, is that you lack most advertisement funds, and you can’t really express to the public the fact you’re a better choice in many cases, than a big bank .