If you buy a municipal bond that yields 6 percent, then it would be the equivalent of a taxable yield of 8 percent.

FORBES: Are Municipal Bonds Currently A Good Investment?

For a taxpayer in the top federal bracket of 35%, a 3% dividend yield is equivalent to a 4% yield on a taxable bond.

FORBES: When Patience Pays

For example, a tax-free yield of 3% would be the equivalent of a 4.6% taxable yield for someone in the 35% bracket, and 4.97% for someone in the 39.6% bracket.

WSJ: Conquering Retirement: The Case for Muni Bonds