Thirty-year muni yield climbs to 5.18%, its highest since 2011, as data-center supply meets redemptions

The benchmark 30-year municipal yield climbed to 5.18%, its highest since at least January 2011, after state and local debt fell 4.4% for the month in a sell-off ETF Trends calls the steepest for munis since 2008. Ten- and 30-year Treasury yields reached their highest levels since 2002 over the same stretch, and ETF Trends reads the move as a rate shock rather than a credit event: municipal credit quality sits near record strength while tax-exempt yields are at their highest in more than a decade.

Supply is where September gets interesting. The usual seasonal issuance wave was compounded, ETF Trends reports, by a newer source of paper: state and local issuers financing the power, grid, water and wastewater infrastructure that data centers require — the data-center buildout this publication has mostly tracked through private project finance, now turning up on the public side of the ledger. That supply ran into retail-heavy mutual funds that had logged consecutive weeks of net redemptions, leaving managers to sell into a thin secondary market.

Open-end funds strike one daily price off matrix marks; muni ETFs traded continuously through the turmoil and showed market-clearing levels in real time. In a month when the secondary market thinned out, that difference adds a third leg to the wrapper thesis: wrapper choice has mostly been a question of fees and distribution, but in fixed income the wrapper also performs a liquidity function, the intraday pricing that lets a buyer transact when dealers step back. It restates September's point, too — a short-dated income overlay does not remove the duration exposure that does the damage in a rate shock.

At 5.18% and an assumed 40.8% top federal rate (37% plus the 3.8% net investment income tax), benchmark paper equates to an 8.75% tax-equivalent yield. Allspring Global Investments' Nicholas Venditti, who heads municipal fixed income there, told ETF Trends on a recent webcast that buyers today are locking in tax-exempt yields he doubts they will regret in one, two or five years. He runs muni money, so the enthusiasm carries the usual asterisk; the tax-equivalent number is the one being sold, and it is a function of the price decline, not of improving credit.

If issuance tied to power, grid and water buildouts keeps filling the calendar while mutual funds keep redeeming, the buyer of last resort in September was whoever showed up intraday, and the ETF wrapper was the vehicle that could. The 30-year yield at 5.18% is the print that tells you whether the rate shock is done.