A 10% risk-free yield? For some, yes.

The headline refers to tax-equivalent yield — the adjusted return on a tax-exempt investment, such as a municipal bond, once you account for the taxes you would otherwise owe on a comparable taxable bond. For investors in the highest federal brackets, and especially those who also pay state or local income taxes, a seemingly modest tax-free coupon can equate to a double-digit pre-tax yield. That is why a muni paying a low nominal rate may look like a bargain to a very high earner while offering little advantage to someone in a lower bracket.

The key point is that the benefit is personal, not universal. Tax-equivalent yield depends on your marginal rate, your state's treatment of the interest, and whether the bond is exempt at the state level as well as federally. Two investors holding the same security can end up with very different after-tax outcomes.

What to watch: current tax brackets and any proposed changes, since shifts in rates alter the math; the credit quality and duration of the underlying issuer; and whether alternative minimum tax rules apply. The comparison only holds against a genuinely similar taxable bond.