HIMU Sits Vulnerable to a Double Risk: Slowing Growth and Stuck Interest Rates

The iShares High Yield Muni Active ETF (CBOE:HIMU) sits in one of the more specialized corners of the bond market: actively managed, below-investment-grade and non-rated municipal debt, wrapped in an ETF and pitched at investors hunting tax-advantaged income that ordinary muni funds cannot match. Shares are around $49 today, with a one-year total return of about 6%. That return is the reason people own it. The risks below are why that return is not guaranteed to repeat.

Why investors hold HIMU

High-yield munis pay more than investment-grade munis because the issuers are weaker: hospital systems with thin coverage ratios, charter schools, land-secured “dirt bonds” tied to specific developments, tobacco settlement bonds, and Puerto Rico paper. The interest is generally exempt from federal income tax, which is the entire pitch. An active manager, in theory, can avoid the worst credits and concentrate in the best risk-adjusted ones. That is the bargain HIMU offers.

The primary risk: credit spreads in a slowing economy

The biggest risk facing HIMU right now is credit deterioration in lower-rated municipal issuers if economic growth keeps softening. The data points are already lining up. Real GDP grew just 0.5% in 2025Q4, with government spending contracting 5.6%, the weakest reading in the BEA’s five-year window. 2026Q1 rebounded to 2.0%, but the volatility itself is the signal. State and local tax receipts, hospital admissions, charter-school enrollment, and project-specific revenues all sit downstream of that economic noise.

The transmission mechanism into HIMU is straightforward. When growth slows and government outlays contract, marginal issuers (a regional hospital, a senior-living project, a special tax district) see revenue compression first. Spreads on those bonds widen, and because the high-yield muni market is thin, prices can move sharply on modest selling. Active management helps at the margin, but it does not insulate the fund from a sector-wide repricing.

The yield curve corroborates the caution. The 10-year minus 2-year Treasury spread has compressed from 0.7% in early February to 0.5% recently, sitting in the 14th percentile of its trailing year. Flattening curves typically precede credit-spread widening in lower-rated debt.

The secondary risk: rates that refuse to fall further

The Fed has cut 75 basis points since September 2025, leaving the upper bound at 3.8%, but it has held there since December 10, 2025. Meanwhile the 10-year Treasury yield is 4.4%, in the 83rd percentile of the past year, and CPI sits at the 90th percentile of its trailing 12-month range. If inflation stays sticky and the Fed pauses indefinitely, long-duration munis lose their tailwind, and any further upward drift in long yields pressures NAV. Without a published duration figure for HIMU, investors should treat the fund as carrying meaningful long-end exposure characteristic of the high-yield muni category.

What to monitor

1. High-yield muni spreads vs. AAA munis. Bloomberg and MMA publish weekly data; a sustained widening of 50 basis points or more above the trailing-year average is the credit signal. Check monthly, weekly during recession scares.
2. The 10-year Treasury yield on FRED (series DGS10). A sustained move above the recent 12-month high near 4.6% would mark fresh duration pressure. Check weekly.
3. State and local tax revenue reports. The Census Bureau’s Quarterly Summary of State & Local Tax Revenue is the cleanest read on issuer fundamentals. Quarterly cadence.
4. BlackRock’s HIMU fact sheet and holdings file. Watch sector concentration in tobacco, healthcare, charter schools, and Puerto Rico; outsized moves in any single sector are the fastest tell. Monthly review.

Bottom line

HIMU’s tax-equivalent yield is doing real work for taxable accounts, and the fund has delivered for the trailing year. The setup that justifies caution comes from a flattening curve, sticky inflation, a paused Fed, and a softening growth backdrop, all of which weigh on the weakest muni credits first. Watchful is the right posture. A clean break wider in high-yield muni spreads would change that.