ⓘ Sources, calibration, and what is modeled vs. observed — click to open
Read this before you quote a number off the muni or corporate curve.
Only the Treasury curve is observed. It is Treasury's own published daily data, 160 trading days, no modeling.
The municipal and corporate curves are the Treasury curve re-priced through a fixed ladder of ratios and
spreads. They are estimates, and they carry two limitations you should know about:
First, the ladder does not move. It is calibrated to mid-August 2026 and held constant across all 160 days.
So when you scrub back to January, you are seeing January Treasuries times August ratios — not the muni market
as it actually traded in January. Credit spreads and muni ratios moved during 2026, and this viewer does not
capture that movement. The day-to-day motion you see on these curves is entirely Treasury motion.
Second, the shapes differ by construction. The AAA municipal benchmark past eleven years is a
yield-to-worst on a 5% coupon callable to a ten-year par call, not a bullet yield. Corporate spreads here are
option-adjusted index levels applied as par spreads. Neither is strictly comparable to a Treasury par yield.
For directional work and for showing a council or a board what tax exemption is worth, this is fine.
For pricing an actual issue, use your financial advisor's live scale.
Use the spread shock slider to stress the ladder. That is the honest way to work with a modeled curve:
not as a single answer, but as a range you can push on.
How the ladders were calibrated. The municipal curve is Treasury multiplied by a muni/Treasury ratio
that rises with maturity — 60% at one year, 68% at ten, 75% at twenty, 83% at thirty. Checked against the
published AAA benchmark for August 17, 2026, that ladder reproduces 3.21% at ten years against a published
3.18%, 3.97% at twenty against a published 3.97%, and 4.41% at thirty against a published 4.39%. It also
sits inside the MMD ratios reported for early August — 64% at five years, 70% at ten, 85% at thirty.
Corporate spreads are added in basis points over Treasury and widen with maturity, which is what credit
curves do: AA runs 22 bp at one year to 68 bp at thirty, A runs 35 bp to 92 bp, BBB runs 55 bp to 135 bp.
These are anchored to the ICE BofA index option-adjusted spreads for August 2026, where BBB was reported
near 97 bp, and cross-checked against Treasury's own High Quality Market corporate curve, which showed
roughly 70 bp over Treasuries at ten years and 83 bp at thirty.
On the taxable-equivalent line. TEY divides the tax-exempt yield by one minus your rate. At 40.8% the
math is unforgiving in the right direction: a 4.41% thirty-year AAA municipal is worth 7.45% to a taxable
investor. That gap is the whole argument for the exemption, and it is why the compare view is the one to
show a council.
On the thirty points. Treasury publishes only eight tenors — 1, 2, 3, 5, 7, 10, 20, and 30 years. Those are
the solid dots. Everything between is interpolated with a monotone cubic fit. The 15-year and 25-year marks
show as hollow dots for that reason, and the stretch between 20 and 30 is the least observed part of the curve.