A proposal to slash dividends paid to private banks that are members of the Federal Reserve system is drawing criticism from the banks. “It sets a bad precedent,” a spokeswoman for the Iowa Bankers Association said. The Independent Community Bankers of America sent a letter to leaders of the U.S. House and Senate on Thursday that is critical of the proposal, which is part of a plan to increase highway funding and offset those costs by cutting the dividend. The letter was endorsed by the Community Bankers of Iowa. Banks are required to purchase stock from the Federal Reserve when they become part of the system. The cost is 6 percent of a bank’s capital. The stock cannot be transferred or sold. Proposals in Congress would cut the dividend paid back to the banks to 1.5 percent from 6 percent, according to a story earlier this year inThe Wall Street Journal. Banks with more than $1 billion in assets would be affected. Four Iowa banks with assets of more than $1 billion are members of the Federal Reserve system.