A Trading Tactic Is Foiled, and Banks Cry Foul

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[The counter-]argument is based on the idea that forcing these transactions out into the open, and forcing those who trade in them to put up margin, will raise the costs for those who use the derivatives. It is at least possible that the opposite will turn out to be true: that as transparency drives down the spreads between the prices at which people are willing to buy and sell derivatives, it will damage the profits of the swap dealers -- generally the big banks -- but benefit the customers. That is what has happened when other markets, like those for corporate and municipal bonds, were opened up to sunlight.