Concept #6 · the investable floor · the pool's real long-vs-short structure · public data only

Most of this pool never moves, so its long posture is defensible. The middling yield is a composition problem, not a duration one.

Strategy lever #6, liability-aware structure, answers two questions book-yield reporting can't: how much of the pool truly must stay short and liquid, and how much is a permanent base that can sit at the long end? We answered it from the County's own six-year cash history, every monthly report, January 2020 through March 2026, no privileged data. The answer reframes the "longest-duration-in-California" finding: the long posture is supported by the County's own flows, and the way to lift yield is not more duration, it's better composition.

The pool by the dollar, what must stay liquid vs. what can run long

$10.5B

total pool · 3/31/2026

$3.48B

liquid buffer the data calls for, 33.1% (1.5× the worst 22.1% withdrawal)

$7.03B

permanent base, 66.9%, the pool's flows never draw down

$1.29B

of that buffer currently sits in cash / money-market

The worst peak-to-trough cash drawdown in 75 months was 22.1% of the pool (2021-04 → 2021-07). At a 1.5× safety margin, a $3.48B (33.1%) liquid buffer covers it with room to spare, which means $7.03B (66.9%) is a permanent base the pool's own history shows is never touched. The $1.29B of cash/MMF is simply the cash slice of the liquid side; the rest of the buffer is short-dated bonds.

The reality check: the pool already runs this way, if anything, a touch too long.

Set the model beside what the pool actually holds today, security by security: $7.45B (70.9%) already sits beyond one year, and only $3.05B (29.1%) is liquid (cash plus everything maturing inside a year). So the pool is already at, slightly past, the prudent long limit: about $0.4B more long, and $0.4B thinner on liquidity, than this floor would set. Two honest conclusions follow, and neither is "extend further."

What the floor analysis actually says

The long posture is validated, not reckless. The longest WAM of any large California county pool looks aggressive on its face, but the County's own cash-flow history shows only ~$3.48B ever needs to be liquid and a $7.03B base never moves. The duration is, structurally, a defensible, liability-matched position, provided it is measured and managed on a total-return basis rather than left to drift.

The one caution is liquidity, not yield. The pool holds ~$3.05B liquid against the ~$3.48B the data prudently calls for, running about $0.4B (≈4% of the pool) thinner on dry powder than ideal. The only "do something" the floor work surfaces is to top the buffer up modestly, not to term more out.

There is no idle-cash yield lever here. Because the base is already at the long end, the "term it out for more yield" idea is already captured, the pool isn't sitting on idle money to deploy. The yield improvement has to come from elsewhere.

So why is the yield middling for the longest duration in the state?

If the pool is already maximally long, extending can't fix the yield. Three things explain it, and only one is permanent:

Amortized-cost lag, now closed. Book yield is 4.25% and the book's market yield, solved street-convention, reported price plus accrued interest, is 4.21%: converged. The low-coupon 2020–21 bonds that once held the book far under the market have largely rolled off, so the lag explains the past, not the present. What remains of the "weak yield" question is posture, that's B and C.

Duration without spread, the real issue. The pool takes rate risk (long) but earns little credit/sector spread: roughly half is federal agencies, plus Treasuries and supranationals, high grade, low yield. It is paid for duration but not rewarded with spread. This is "uncompensated carry," in plain dollars.

The curve penalized being long (2022–24). Through the inversion, short cash out-yielded long bonds, so the long posture cost yield. Our backtest shows it (below): running the base long trailed staying short by 1.59% (~$112M) over the window. The curve has since normalized.

What we'd do, earn the reward for the duration already carried

Add high-grade spread at the same quality. Rotate part of the agency/Treasury weight into investment-grade corporates, supranationals (World Bank / IFC / IADB, also EIP-positive), and short, high-grade ABS / agency-CMBS, all within §53601. More yield per unit of duration, no step down in credit. This is the biggest safe-yield lever.

Capture roll-down and manage to total return. Sit at the steepest part of the 0–5 year curve and run the core against a duration-matched index, so the duration the pool already carries is monitored and rewarded, not a set-and-forget bet.

Let the legacy book roll, and use the no-loss runoff. Low-coupon ZIRP-era bonds reinvest at higher rates as they mature; where they trade at or above book, rotate sooner into spread product. Book yield converges up toward the ~4.6% the market already implies.

The two pictures behind this

Pooled balance vs. a floor at 66.9% of the pool; worst drawdown 22.1%

The navy line is the pool's actual balance over 75 months; the gold dashed line is the 66.9%-of-pool floor. The balance never approaches it, the worst fall was 22.1%, and the 33.1% buffer (1.5×) sits comfortably above the deepest trough. This is the evidence the long posture is supported.

Growth of $100: base run long vs. kept short (3-mo T-bill roll)

Growth of $100: the base run long (the pool's own total return, navy) vs. kept short in a 3-month T-bill roll (gold). Over this window the long path finished behind, $117.23 vs. $118.82, a 1.59% gap, the 2022 rate shock and inversion at work (NAV troughed at 95.857). The lesson isn't "go short"; it's that duration only pays when it's managed to total return, and that the safe-yield gains live in spread and roll-down, not in more length.

The bottom line: if we're going to be the longest, let's be the strongest.

Is the longest duration in California reckless? No, the County's own cash-flow data backs it, so long as it is measured and managed to total return. The yield is middling not because the pool is too short but because it carries duration without the spread that should reward it, on a book still lifting out of the zero-rate era. The fix is composition and active total-return management, precisely the work an independent evaluation, and a specialist running a managed core, would deliver. One housekeeping note stands out: liquidity is running modestly thin against the buffer the data calls for.

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