Latest / The Fiscal Policy Podcast with Fexingo: Government Budgets, Stimulus, and Public Spending / Why Government Bonds Have a Hidden Tax Cost
Transcript
- Lucas: So there's this number that always bugs me when I look at government borrowing — the size of the Treasury market is about twenty-eight trillion dollars. That's the biggest bond market in the world by a wide margin. Luna: Right, and most people think of those bonds as the safest investment on earth. But safe doesn't mean simple. Lucas: Exactly. And there's a layer of complexity that almost never gets talked about in the fiscal policy conversation — the tax treatment. Specifically, the fact that interest on Treasury bonds is fully taxable at the federal level, while interest on municipal bonds is exempt. Luna: That's a pretty big difference. And it's not just an academic point — it changes who buys what and at what price. Lucas: If walking through government finance with us has made something click — maybe today's point about hidden tax costs — the way this show stays ad-free and independent is listener support. It's buy me a coffee dot com slash fexingo, and that's it. Luna: Yeah, it honestly makes a difference. And it keeps us from having to run ads in the middle of explaining bond yields. Lucas: So back to the bonds. Let's take a concrete example. Say you're a high-earner in California — top federal bracket is thirty-seven percent, plus state income tax. You're looking at a ten-year Treasury yielding four and a half percent. But after federal tax, your after-tax yield is closer to two point eight percent. Luna: Ouch. And if you buy a California municipal bond instead — same maturity, maybe yielding three point five percent — that interest is exempt from both federal and state tax. So your after-tax yield is actually higher. Lucas: That's the tax-equivalent yield concept. A three-point-five-percent muni can be worth more than a four-point-five-percent Treasury, depending on your bracket. The formula is straightforward — tax-equivalent yield equals the tax-exempt yield divided by one minus your marginal tax rate. Luna: So for someone in the thirty-seven percent bracket, that three-point-five percent muni is equivalent to a taxable yield of about five point six percent. That's a full percentage point above the Treasury. Lucas: Right. And that gap is essentially a hidden tax cost borne by the Treasury bondholder — or, looked at another way, a subsidy from the federal government to state and local governments, because it lets them borrow more cheaply. Luna: How much cheaper? I've seen estimates that the tax exemption lowers municipal borrowing costs by about fifty basis points on average. Lucas: That's the ballpark. And it adds up — the total value of the federal tax exemption for municipal bonds is something like thirty to forty billion dollars a year in forgone federal revenue. That's a tax expenditure, just like the mortgage interest deduction, but it's much less discussed. Luna: So the federal government is effectively subsidizing state infrastructure projects through the tax code, rather than through direct grants. Lucas: Exactly. And that creates some interesting distortions. For one, it means the benefit of the subsidy goes disproportionately to high-income investors who are in the top brackets. Lower-income investors get less benefit from tax exemption because their marginal rate is lower. Luna: That seems regressive. The people who need tax-advantaged income the most get the least benefit. Lucas: It is. And there's another distortion: because munis are so attractive to high earners, the market for Treasuries ends up being dominated by different types of buyers — pension funds, foreign central banks, insurance companies that are tax-exempt or have different tax considerations. Luna: So the tax treatment effectively segments the bond market. That has implications for liquidity and pricing. Lucas: Right. And one more layer — when the Federal Reserve buys Treasuries, as it did during quantitative easing, it's buying from a market where the tax distortion is already baked in. That complicates the transmission of monetary policy. Luna: I want to push back a bit. Is this complexity intentional? Or is it just an accident of policy layering over decades? Lucas: I think it's mostly accidental. The income tax was introduced in 1913, and the exemption for municipal bonds was established by the Supreme Court soon after, based on the doctrine of intergovernmental tax immunity. It wasn't a carefully designed subsidy — it was a constitutional principle. Luna: So we're stuck with a system that was essentially a legal byproduct. And it's persisted because it benefits powerful constituencies — states, municipalities, and wealthy investors. Lucas: Exactly. There have been proposals to cap or eliminate the exemption, but they never go anywhere. The last serious attempt was in the Tax Reform Act of 1986, which placed some limits on private-activity bonds, but the core exemption survived. Luna: And an interesting wrinkle — some states also tax out-of-state municipal bonds. So if you live in New York and buy a California muni, you might pay state tax on it. That further fragments the market. Lucas: Good point. That creates a home-state bias in municipal bond portfolios. Investors tend to buy bonds from their own state to get the double exemption, which reduces diversification. Luna: So what's the bottom line for the average listener? Should they care about this? Lucas: I think so, because it's a reminder that the cost of government borrowing isn't just the interest rate on the bond. The tax code creates winners and losers, and those costs are passed on to taxpayers in ways that aren't obvious. If you're an investor, you should always compute the after-tax yield of any bond you buy. And if you're a voter, you should know that your state's infrastructure is being partly financed by a tax break that mostly helps the wealthy. Luna: And that the size of that tax break — roughly thirty to forty billion a year — is a policy choice that rarely gets debated. Lucas: Right. So next time you hear about the twenty-eight trillion dollar Treasury market, remember there's a hidden tax cost embedded in every yield. It's not just about the rate — it's about who pays, who benefits, and what that means for the broader fiscal picture. Luna: Makes you wonder what other invisible costs are lurking in government finance. Lucas: That's a thread we'll keep pulling.