A new working paper from Man Group’s Panashe Bera and Kristina Hooper, and Duke University’s Fuqua School of Business’ & NBER’s Campbell R. Harvey, draws a sharp line between two high-inflation environments that portfolio managers too often treat as one. Published in October 2026 and available at SSRN, the study spans 107 years of monthly US data and delivers a regime-based framework with direct implications for how advisors think about inflation-conditional asset allocation.
The paper's argument is methodological as much as empirical. Bera, Harvey, and Hooper contend that analyzing asset sensitivity to inflation alone misses a critical variable: the state of economic growth running alongside it. They construct a three-regime taxonomy, classifying each month from January 1919 through May 2026 as Overheating (high inflation with above-trend growth), Stagflation (high inflation with weak growth), or Contained (the baseline, absent elevated inflation). Unlike prior work relying on fixed thresholds or retrospective NBER recession dating, the framework uses real-time signals built from rolling 10-year reference windows for both CPI and industrial production.
The design includes deliberate safeguards against lookahead bias. A two-month publication lag is applied to both macroeconomic series, and a raw state must persist across three consecutive months before it is confirmed. Together, these filters ensure the classification "avoids lookahead bias to the best of our abilities," as the authors describe it, while acknowledging that historical macroeconomic data remains subject to revision.
The performance data is stark. The Contained baseline accounts for 72.2% of all months, with the 60/40 portfolio earning 9.0% annually in real terms. In Overheating, that figure falls to -1.3%. In Stagflation, it falls to -0.2%. The S&P 500 earns 12.4% real annually in Contained periods, compared to 0.7% in Stagflation and -0.2% in Overheating. The authors observe that a confirmed Stagflation period may combine further losses with a partial recovery, as markets anticipate improvement even while reported growth remains weak, a dynamic the regime averages blend together.
Nominal bonds carry the heaviest burden during Overheating, where rising real rates and inflation expectations compound simultaneously. The 30-year Treasury loses 6.4% annually in real terms under Overheating versus -1.4% in Stagflation. TIPS provide meaningful but partial protection in both regimes, returning 2.4% real in Overheating and 1.8% in Stagflation, against 2.8% in Contained periods. Bera, Harvey, and Hooper note this is consistent with protection rather than immunity.
Among alternatives, the findings are more differentiated. Gold returns 14.2% in Overheating and 9.4% in Stagflation. Multi-asset trend following delivers 7.4% and 13.5% in those same regimes, narrowing the gap with its 14.0% Contained average. An equal-weighted composite of long-short equity factor strategies outperforms its Contained baseline in Stagflation, with quality, profitability, size, and bet-against-beta factors leading.
The paper's second analytical layer conditions returns on the direction of inflation. Using a six-month acceleration signal, the spread in Overheating is extraordinary. Accelerating inflation in that regime produces a 60/40 loss of 7.7% annually in real terms; decelerating inflation produces a gain of 7.5%. That is a 15.2 percentage point separation. In Stagflation, acceleration matters less, though the directional tilt persists. Gold is a consistent exception, performing better in accelerating inflation across both regimes.
Three historical case studies close the empirical section: the Vietnam War and Great Society inflation from 1966 to 1971, the OPEC embargo period from 1973 to 1976, and the second oil shock and Volcker disinflation from 1978 to 1981. Each episode reveals that commodity and precious metals gains tended to concentrate in the pre-confirmation run-up to Stagflation, not during the confirmed regime itself. The authors note that an allocation established after confirmation faces a fundamentally different opportunity set from one positioned during the initial inflationary shock. The 2023 to 2024 period is classified as a new Stagflation episode under their real-time framework, following the post-pandemic Overheating classification of 2021 to 2022.
Five Key Takeaways for Advisors and Investors
- High inflation is not a single environment. Overheating and Stagflation impose materially different costs on portfolios, and the distinction determines which assets provide meaningful diversification.
- The 60/40 portfolio struggles under both inflation regimes, but the damage differs. Overheating is more destructive for nominal bonds; Stagflation widens credit spreads and keeps growth weak simultaneously.
- Inflation direction matters as much as its level. In Overheating, decelerating inflation is historically associated with recovery-level portfolio returns; accelerating inflation produces severe real losses.
- Trend following and long-short equity factors have historically provided diversification across both Stagflation and Overheating, and that resilience holds across both acceleration subsamples.
- Timing relative to regime confirmation is critical. Commodity and precious metals gains have historically front-run confirmed Stagflation episodes, not followed them. Advisors acting after confirmation are working with a different opportunity set than those who positioned earlier.
Footnote:
1 Bera, Panashe, Campbell R. Harvey, and Kristina Hooper. "Stagflation and Asset Management." SSRN Working Paper, 23 Oct. 2026, https://papers.ssrn.com/sol3/papers.cfm?abstract_id=7662619.
