Why normalize the classic Buffett Indicator
The classic Buffett Indicator compares total U.S. equity market capitalization with GDP. That ratio can rise because investors are paying more for a given level of earnings, but it can also rise while corporate profit margins are unusually high.
NBI divides the market-cap-to-GDP ratio by the 24-month simple moving average of S&P 500 profit margins. For the same market-cap-to-GDP ratio, a higher profit-margin denominator lowers NBI's raw reading, while a lower margin raises it.
What the normalization is trying to isolate
If two periods have the same market-cap-to-GDP ratio but one has materially higher profit margins, NBI treats the high-margin period as less expensive. The 24-month average dampens short-lived margin spikes and drops instead of letting one quarter dominate the adjustment.
This does not make profit margins irrelevant. It makes the profitability environment an explicit part of the valuation comparison rather than leaving it embedded inside the headline market-cap-to-GDP ratio.
Where NBI can mislead
Profit margins can change structurally, and a 24-month average necessarily reacts with a lag. Market capitalization and GDP also measure different economic universes, so the ratio is an approximation rather than a perfectly matched numerator and denominator.
NBI is best treated as long-horizon valuation context. A high reading does not identify a near-term market top, and a low reading does not identify the exact start of a durable rally.
How NBI differs from CARP
NBI adjusts market-cap-to-GDP for profitability. CARP instead compares a cyclically adjusted equity earnings yield with Treasury yields.
When the two disagree, the difference is informative: profit-margin normalization and the interest-rate backdrop are pulling the valuation picture in different directions.
Low example
52.5
Apr 8, 2025
Median score
79.3
Selected sample
Average score
79.2
Selected sample
High example
100.0
Sep 24, 2025
Regime frequency in this sample| Regime | Observations | Share |
|---|
| Bargain | 0 | 0.0% |
| Inexpensive | 0 | 0.0% |
| Fair | 8 | 1.8% |
| Expensive | 305 | 69.6% |
| Ruinous | 125 | 28.5% |
These frequencies describe the selected historical sample. They are not probabilities for future returns or market turning points.
