I suspect the proposed tax on financial transactions wouldn’t raise as much money as projected, because it might put a major damper on speculative activity by banks. While the proposed tax appears to be very small, the reason it would raise so much money is that the volume of financial transactions is so high. Trillions of automated transactions that collectively make billions of profit for banks might actually make only a small profit per transaction. The tax might thus be a larger part of the profit on each transaction, making certain kinds of financial churn no longer profitable.
I think this is likely a good thing. But there may be better ways to achieve the same goal.
Robin Hood, Robin Hood, with his band of men
Feared by the bad, loved by the good
Robin Hood, Robin Hood, Robin Hood