The S&P 500 can finish the day green while most of its members fall. Five or six giant companies carry the index on their shoulders, and the other several hundred quietly drift lower. If you only watch the headline number, you never see it happen.
The Market Mood Index exists to surface exactly that — whether a market move is broad or narrow, and how today's reading compares to a decade of history. This article explains how it is built, why its mood bands are set where they are, and, just as importantly, what it cannot tell you.
What the Market Mood Index Is¶
The Market Mood Index is a single number from 0 to 100, updated every trading day after the US close, that summarizes how broadly bullish or bearish the market is behaving.
It is built entirely from price action. There is no news scraping, no social-media scoring, no paid sentiment feed and no opinion involved. It reads what stocks are actually doing — how many are rising, how many sit above their long-term trend — and turns that into one figure. It is computed in-house across a curated universe of 189 large, sector-balanced US stocks, plus one external input: the VIX, the market's volatility gauge.
Why a Single Index Price Can Mislead You¶
The most-quoted market numbers — the S&P 500, the Nasdaq 100 — are capitalization-weighted. The biggest companies move the index the most. When a handful of megacaps rally, the index can climb even as the typical stock is falling.
Breadth is the antidote. Breadth measures participation: out of all the stocks you are tracking, how many are actually going up? A rally where 80% of stocks participate is healthy. A rally where the index rises but only 40% of stocks are above their 200-day average is narrow, fragile, and historically a late-cycle warning. Analysts call that gap an advance/decline divergence.
The Market Mood Index is deliberately equal-weighted — one stock, one vote. A trillion-dollar company and a mid-cap each count exactly once. That is what lets the gauge show "Caution" while a cap-weighted index is still making new highs.
The Six Ingredients¶
The score is a weighted blend of six measurements. Each is normalized to a 0–100 scale where 0 is bearish and 100 is bullish:
- Breadth, 1-day — 10% weight. The share of the 189 stocks that closed higher today. The rawest read on participation, and the noisiest, so it carries the smallest weight.
- Breadth, 5-day average — 15% weight. The same measure smoothed over a trading week, which strips out single-day noise.
- Breadth, 20-day average — 20% weight. Breadth smoothed over roughly a month — a much steadier signal of the prevailing tide.
- Stocks above their 50-day moving average — 20% weight. What fraction of the universe is trading above its medium-term trend line.
- Stocks above their 200-day moving average — 20% weight. The same idea for the long-term trend — the classic dividing line between a bull and bear posture for an individual stock.
- VIX, inverted — 15% weight. The VIX measures expected volatility; high VIX means fear. We take its percentile over the trailing year and invert it, so calm markets push the score up and panic pushes it down. The VIX is the only ingredient that comes from outside the stock universe — it acts as an external fear cross-check.
The weighting is intentional. The noisy 1-day breadth gets the least say; the medium-term participation signals — 20-day breadth and the two moving-average measures — dominate, because that is where the durable signal lives.
From Six Numbers to One Score¶
The arithmetic is plain: each component is scored 0–100, multiplied by its weight, and the six results are added together. The total is clipped to stay within 0–100. There is no machine learning and no hidden tuning — the formula is the formula, and it is published.
The Seven Mood Bands¶
A raw number is hard to read, so the score maps to one of seven mood bands, running red to green:
- Capitulation — 0 to 30. Wholesale selling; fires about 5% of the time.
- Fear — 31 to 43. Broad weakness; about 15% of the time.
- Caution — 44 to 52. Below-average participation; about 20%.
- Neutral — 53 to 59. The market's normal middle gear; about 20%.
- Optimism — 60 to 65. Healthy, broad strength; about 20%.
- Greed — 66 to 70. Stretched to the upside; about 15%.
- Euphoria — 71 to 100. Extreme breadth; about 5% of the time.
Those cutoffs are not round numbers chosen by intuition. They are calibrated against history — and the story of how is worth telling honestly.
Why 50 Is Not "Neutral"¶
The instinct is to treat 50 as the neutral midpoint. It is not, and assuming it is would make the gauge structurally bearish.
Stock returns have a positive long-run drift — the equity risk premium, the reason buying stocks pays over time. Over years, that drift pushes breadth and trend participation upward. When we replayed the modern-era history, the average score came out at 54.7, not 50. A gauge that called 50 "neutral" would therefore spend most of its life flashing mild optimism for what is really just an ordinary market.
There is a second asymmetry. Equity returns are negatively skewed: markets crawl up the stairs and fall out the window. Crashes are fast and deep; melt-ups are slower and shallower. So the score's floor sits lower than its ceiling. In the calibration window the reading ranged from about 12 at the worst to 80 at the best — a long left tail, a short right one. The bands are spaced to match that real shape rather than a tidy symmetric one. That is why "Neutral" sits at 53–59, not centred on 50.
How the Bands Were Calibrated — The Honest Version¶
The current bands are the third version. The first two are instructive failures.
Version 1 used hand-picked, round-number bands — Euphoria at 86–100, and so on. When we replayed them against decades of history, they were badly miscalibrated: the Euphoria band fired 0% of the time in 40 years, and a single optimistic band swallowed nearly half of all readings. Tidy numbers, useless gauge.
Version 2 fixed that by setting the bands to actual historical percentiles, using more than 9,000 daily snapshots replayed back to 1986. But it had a quieter flaw: only 60 of the 189 stocks in today's universe existed in the data that far back. The historical distribution was dominated by decades-old survivors — a textbook case of survivorship bias.
Version 3, the current calibration, tightened the rule: a historical day only counts if at least 80% of today's universe was already publicly traded then. That trades roughly 30 years of skewed history for about 10 years of genuinely comparable signal — the window from November 2016 to May 2026, 2,253 daily snapshots. The bands are the percentiles of that distribution, so each band fires at roughly its intended frequency.
It is a smaller dataset, deliberately. A clean decade beats a biased four.
What the Index Cannot Tell You¶
A gauge is only useful if you know its limits:
- It is not the cap-weighted market. Because it is equal-weighted across a curated list, it will sometimes disagree with the S&P 500 — and that disagreement is the point, not a bug.
- 189 stocks are not "the market." The universe is a sector-balanced selection. It correlates strongly with broad indices but is not identical to any of them.
- The bands carry inherited drift. They are calibrated on a decade that leaned bullish. A long structural bear market — Japan after 1990, say — would slowly make the gauge read "too optimistic" until it was recalibrated.
- Euphoria is not a buy signal. It is coloured deep green, but historically a high reading is a top-of-cycle warning, not an invitation. The score never even reached 85 across decades of replay, so a reading in the high 70s is rare and worth respecting rather than chasing.
Reading It in Practice¶
The single most useful habit is to read the Market Mood Index alongside the headline index, not instead of it. When both rise together, a rally is broad and well-supported. When the index climbs but the mood gauge slips toward Caution, fewer and fewer stocks are doing the lifting — historically a signal to pay closer attention.
The gauge is updated automatically every weekday after the US close and is free to view — there are no paid data feeds behind it. If you want a companion measure aimed at outright crash risk rather than day-to-day participation, our Bubble Watch methodology covers the index built for that question.
The Market Mood Index is an analytical tool for understanding market conditions. It is not investment advice, and no single indicator can predict market direction. Always do your own research and consider your own circumstances before making investment decisions.