On Sept. 17, the morning after the Federal Reserve raised its benchmark rate for the first time since 2023, the Treasury sold $19 billion of 10-year TIPS at a real yield of 2.653%, the highest for that maturity at auction since October 2008. In theory, that should make stocks harder to own.
But the S&P 500 closed at 7,744.06 on Oct. 15, up 16.8% from a year earlier per FRED index data, even as the 10-year real yield rose from 1.71% to 2.78%, near its highest level since the 2008 financial crisis. Did stock investors ignore the bond market? The arithmetic says no.
The Multiple Shrank 15% And The Index Still Rose 17%
An index price is two numbers multiplied together. One is expected earnings per share; the other is the multiple investors pay for them, and separating them shows a textbook repricing that earnings outran.
FactSet's Oct. 17, 2025 report put the S&P 500's forward 12-month P/E at 22.4. Its latest Earnings Insight, dated Oct. 16, 2026, puts it at 19.0, below its five-year average of 19.8.
Dividing price by multiple implies forward earnings of about $296 a share a year ago and $408 now, and a 15% smaller multiple applied to 38% more earnings produces almost exactly the 17% price gain. Rates did bite. The earnings boom bit harder.
Chris Carpentier, a senior investment strategist at State Street Investment Management, reached the same conclusion in a Sept. 21 note. "Markets are still responding to higher discount rates in a manner broadly consistent with financial theory," he wrote.
Two Measures Of The Cushion Point Different Ways
The equity risk premium (ERP) is the extra annual return investors demand for holding stocks instead of a risk-free bond, and when it runs thin, a modest rate shock can erase months of gains. Nobody observes it directly.
The simplest estimate subtracts the real yield from the forward earnings yield, the inverse of the P/E. At 19.0 times earnings, that yield is 5.26%, or 2.48 percentage points above the TIPS yield, compared with 2.75 points a year earlier, when real yields were more than a full point lower. The cushion narrowed by 0.27.
Aswath Damodaran, a finance professor at NYU Stern, gets a different reading from his cash-flow model. His implied ERP series rose to 4.20% on Oct. 1 from 3.78% a year earlier, even as the Treasury rate he uses climbed to 5.29% from 4.16%. His trailing cash-yield version slipped to 3.70% from 4.01%, closer to Carpentier's view that the premium "has compressed and remains at lows."
Forward-earnings measures depend on analysts being right, and cash-yield measures assume the past year repeats; neither shows stocks as cheap relative to TIPS. The method decides the answer.
Two Chipmakers Carry 9 Points Of Earnings Growth
The earnings lift is narrow. FactSet's blended third-quarter growth rate is 29.0%, but exclude Micron Technology Inc. (MU) and NVIDIA Corp. (NVDA) and it falls to 20.0%.
Growth should slow. FactSet consensus projects 16.0% for calendar 2027 but only 2.8% for the second quarter of 2027 as year-ago comparisons stiffen, while sector multiples range from 13.3 times forward earnings for Energy to 23.4 for Consumer Discretionary.
The sensitivity is steep. Hold the 2.48-point cushion constant and leave earnings estimates flat, and a quarter-point rise in the real yield implies a P/E near 18.1, or about 4.5% lower prices. A half-point rise implies roughly 17.4 times earnings, an 8.7% decline, while a half-point drop supports about 21 times.
A Quarter-Point Hike Does Not Reopen Hormuz
CBS reporter Richard Escobedo put the problem plainly at the Sept. 16 press conference. A quarter-point hike, he told Chair Kevin Warsh, "does not reopen the Strait of Hormuz." Warsh replied that the Fed "cannot affect any individual price" but can keep relative price changes from broadening, the official transcript shows.
The September CPI report shows the gap. Headline inflation hit 3.7%, with gasoline up 34.2% over 12 months, while core ran at 2.6%. Regular gasoline averaged $4.33 a gallon in the week of Oct. 12, up from $3.06 a year earlier, EIA weekly data show, and the CPI print briefly lifted rate-hike bets, MarketDash reported.
The bond market is pricing the shock as temporary. The 10-year breakeven rate, the inflation rate at which TIPS and ordinary Treasuries of the same maturity return the same, stood at 2.35% on Oct. 16, next to the Fed's median projection of 2.3% inflation for 2027 on its preferred PCE gauge.
Warsh listed this among the Fed's aims: ensuring "that inflation compensation in market prices stays low." For investors, that sets the bar. TIPS beat nominal 10-year Treasuries only if inflation averages more than about 2.35% over the decade, and Warsh noted that inflation has run above target for more than five years.
Inflation protection is not price protection. The iShares TIPS Bond ETF (TIP) shows a 2.81% real yield and a 6.19-year effective duration, yet its net asset value total return was negative 0.95% year to date as of Oct. 15. Real yields rose 0.84 points this year, and that duration implies roughly a 6% price loss per full point.
What The 2.8% Hurdle Means For A Portfolio
A risk-free real return near 2.8% now sets the bar for every risk asset, and stocks clear it by a narrower margin than a year ago.
- Measure stocks against the real yield. The forward earnings yield minus the 10-year TIPS yield, now 2.48 points, is a workable cushion gauge; FactSet's weekly revisions show which way it is moving.
- Match the instrument to the date. Individual TIPS held to maturity lock in their real yield; a fund such as TIP never matures, so its price moves with real yields. Under TreasuryDirect rules, principal changes may affect federal taxes yearly, so account location matters.
- Check allocation drift. A stock-and-TIPS mix set a year ago, such as one built with the State Street SPDR S&P 500 ETF Trust (SPY) and TIP, has likely drifted toward stocks. Written rebalancing bands decide when drift becomes a trade.
- Watch the next catalysts. FactSet lists Oct. 21 for the first "Magnificent 7" reports, and the Federal Open Market Committee meets Oct. 27-28. Prediction-market traders put October hike odds at 14%.
Equities absorbed higher real yields because earnings grew faster than the discount rate rose; if that reverses, the earnings line will show it first. Stocks now compete with a specific number.
At the Oct. 15 real yield, $100,000 placed in a 10-year TIPS and held to maturity compounds to about $131,500 in today's purchasing power, before taxes.
