Long Bonds vs S&P 500

TLT is the iShares 20+ Year Treasury Bond ETF. It tracks the ICE U.S. Treasury 20+ Year Bond Index, holding a portfolio of US Treasury securities with remaining maturities of at least 20 years. As of early 2026 it manages approximately $41.8 billion and carries a duration of roughly 17 to 18 years, making it the most rate-sensitive mainstream Treasury ETF. Expense ratio is 0.15 percent.

SPY is the SPDR S&P 500 ETF Trust, tracking the S&P 500 index of 500 large-cap US stocks. Expense ratio 0.0945 percent. Both ETFs are highly liquid, with SPY averaging hundreds of billions in daily notional volume and TLT averaging over a billion dollars daily. They are the textbook vehicles for expressing stock-bond allocation views in a single line item each.

For over five decades, the 60/40 portfolio (60 percent equities, 40 percent long-duration bonds) has been the default balanced allocation for individual investors and target-date funds. The framework rests on the observation that stocks and long bonds historically have low or negative correlation, so the bond allocation dampens equity drawdowns without sacrificing too much long-run return.

Against the SPY/TLT benchmark, a 60/40 portfolio from 1976 to 2021 delivered roughly 9 percent annualized returns with drawdowns substantially shallower than 100 percent equities. The worst single-year return through 2021 was approximately negative 20 percent (2008). That historical track record is what made 60/40 the default, and what made 2022 such a shock to the framework's reputation.

From the mid-1990s through 2021, TLT and SPY had a reliably negative correlation on monthly timescales, typically in the range of negative 0.2 to negative 0.5. The mechanism was monetary policy: in growth scares, the Fed would cut rates, boosting bonds and hurting stocks initially before the rate cuts supported equities. In inflation scares, the Fed would hike rates, hurting bonds but not usually enough to overwhelm equity growth.

This inverse correlation is the foundation of 60/40 diversification. It assumes the Fed is the dominant macro driver and that inflation is anchored enough that rate movements respond to growth more than to inflation. When inflation becomes the dominant driver (as in 2022 and the 1970s), both rates and discount rates rise, and both bonds and stocks fall together. The correlation flips positive and diversification disappears.

The COVID crash of March 2020 was a textbook demonstration of the TLT hedge working at maximum intensity. SPY fell approximately 34 percent peak to trough from February 19 to March 23, 2020. TLT rallied to an all-time high near $179.70 on March 9, 2020, a gain of roughly 20 percent from pre-COVID levels, as investors fled to Treasury safety and the Fed cut rates to zero and initiated emergency QE.

A 60/40 portfolio during that window drew down approximately 20 percent, meaningfully less than the 34 percent pure equity drawdown. This episode reinforced the 60/40 framework in the minds of allocators and set the stage for complacency about stock-bond correlation heading into 2022. The hedge worked so well in 2020 that many investors assumed it would continue to work in the next crisis without examining what kind of crisis it was.

The 2022 Federal Reserve tightening cycle was the most aggressive in four decades, with the federal funds rate rising from near zero in March 2022 to 4.375 percent by year-end. The 10-year Treasury yield rose from 1.51 percent to 3.88 percent. TLT fell approximately 33 percent for the year, its worst calendar year on record. SPY fell approximately 18 percent for the same year.

For a 60/40 portfolio, the result was approximately negative 17.5 percent, the worst year since 1937 and the fourth worst in 200 years. It was the first calendar year since 1969 in which both US stocks and US bonds had negative returns. The failure was driven by inflation: the Fed's response to persistent high inflation forced rates higher faster than growth could absorb, and both asset classes repriced lower simultaneously. Anyone who had treated the 60/40 framework as unconditionally diversifying learned an expensive lesson that year.

The 60/40 portfolio recovered through 2023 (approximately plus 17 percent) and 2024 (approximately plus 12 percent). The recovery was driven primarily by the equity side: SPY returned roughly 26 percent in 2023 and 25 percent in 2024. TLT contributed modestly, with roughly flat 2023 and a small positive 2024 as the Fed began cutting rates in September 2024.

As of April 2026, TLT trades near $86.55, still approximately 50 percent below its March 2020 all-time high near $179.70. A full recovery in TLT would require the 10-year yield to fall back toward the 1 to 1.5 percent range, which is not the current trajectory. The 60/40 framework has recovered in total portfolio terms primarily because equity gains have been large, not because the bond sleeve has returned to form.

TLT's roughly 17-year duration means that for every 100 basis point move in its reference yield, the fund's NAV changes by approximately 17 percent in the opposite direction. A move of the 20+ year Treasury yield from 4 percent to 5 percent produces roughly negative 17 percent on TLT. This sensitivity is why TLT had a much worse 2022 than intermediate-duration bond funds: the 33 percent loss corresponded to roughly a 200 basis point yield rise combined with the non-linear convexity effects of duration at high rates.

For portfolio construction, TLT is not equivalent to shorter-duration Treasuries like IEF (7-10 year, duration ~7) or SHY (1-3 year, duration ~2). TLT provides the most hedge per dollar allocated in classic equity-downturn scenarios where the Fed is cutting, but it also carries the most risk when rates rise. Investors seeking a bond hedge without the full duration exposure of TLT often use IEF or a duration-tiered allocation across maturities.

Research from multiple fixed-income desks shows the stock-bond correlation has three regime modes. In a growth-dominated regime (Fed reacts to growth, inflation anchored), correlation is negative around negative 0.3 and bonds hedge equities. In an inflation-dominated regime (Fed reacts to inflation, growth secondary), correlation is positive around plus 0.4 and bonds fail as a hedge. In a policy-dominated regime (Fed forward guidance drives both), correlation can swing sharply between regimes on central bank communications.

The post-2022 period has been transitioning out of the inflation regime back toward the growth regime. The rolling 6-month correlation between TLT and SPY flipped from positive 0.5 in 2022-2023 to near zero by mid-2024 and has been slightly negative (around negative 0.2) through 2025-2026. The hedge is partially restored but not as strong as the 1995-2021 average of negative 0.3.

The traditional 60/40 is increasingly questioned by institutional allocators. Alternatives that have gained traction include 70/30 (more equity-heavy), 50/30/20 with alternatives (private equity, gold, commodities), risk-parity approaches that weight asset classes by volatility contribution rather than dollar value, and all-weather allocations (equities, bonds, gold, commodities, inflation-linked bonds) that seek to diversify across inflation regimes as well as growth regimes.

For a 60/40-like exposure using TLT specifically, a common modification is to replace TLT with a shorter-duration bond fund or a mix of TLT and TIP (inflation-linked Treasuries) to hedge both growth risk (via duration) and inflation risk (via TIPS). A 60 percent SPY / 30 percent TLT / 10 percent TIP allocation would have been materially less painful in 2022 than pure 60/40 while delivering similar long-run returns.

The primary question is whether the 2026 Iran war and Strait of Hormuz disruption re-introduces an inflation-dominated regime. If energy-driven inflation forces the Fed to hold rates higher for longer, TLT faces renewed pressure while SPY may also struggle on margin compression. That regime would look like a mini-2022, though smaller in magnitude.

Secondary signals to watch include the 10-year Treasury yield level (above 4.5 percent is pressure on TLT), the shape of the yield curve (a re-flattening from current 52 bps positive would warn of recession risk, which paradoxically would be good for TLT), and realized inflation versus expectations (above 3 percent realized would reopen the 2022 playbook). For allocators, the question is whether to size TLT based on its 1995-2021 hedging properties or on its 2022 failure-mode, and honest practice is probably a bit of both depending on the current macro regime read.