Market cap to GDP ratio
Also written Market capitalization to GDP · Market cap/GDP · Buffett indicator
The market capitalisation of all listed companies divided by the economy's GDP, times 100 — used to judge whether a whole market is cheap or expensive against its own history or its peers.
In plain language
To judge one stock, an analyst compares its ratios with those of its peers. P/E, EV/EBITDA, price-to-sales.
The market cap to GDP ratio does the same job for a whole country. Add up what the stock market is worth. Divide by what the economy produces in a year. Multiply by 100.
The comparison is then made two ways: against that country's own past levels, or against other countries.
The idea behind it is simple. Price eventually reflects value. So a cheap-looking market should go on to earn better returns, and an expensive-looking one should do worse.
Managers use it to time a tactical shift into or out of equity — buying when the ratio is low and selling when it is high.
How it works
What it is for (section 18.14.3). The ratio determines whether a country is undervalued or overvalued against (i) its own historical values or (ii) its peer countries. The assumption in both cases is that price would adjust itself to reflect value, so undervalued markets generate superior returns and overvalued markets underperform. It is also used to predict the expected return from a market.
The workbook's thumb-rule table — and it labels it, in its own words, only a thumb rule:
| Market cap to GDP | Interpretation |
|---|---|
| Less than 50% | Undervalued |
| 50% to 75% | Moderately undervalued |
| 75% to 90% | Fairly valued |
| 90% to 110% | Moderately overvalued |
| More than 110% | Overvalued |
How managers act on it. The workbook's illustration: portfolio managers track this ratio for a fresh tactical allocation when the percentage is, for example, below 50%, and sell when the ratio moves beyond 100%.
Why the two inputs are comparable. Earnings in a P/E ratio are shaped by business outlook, capital structure, quality and governance, research and development, and brand and marketing. GDP likewise reflects the various constituents of an economy, and GDP data goes through serious scrutiny by analysts, economists, governments and inter-governmental agencies.
The workbook's own charts. For the US it uses the Wilshire 5000 index as the market capitalisation measure, because it is broader than the S&P 500 or the Dow Jones 30 and reflects most publicly traded US companies. Its chart for India shows the Indian market cap to GDP ratio as lower than the US ratio.
The formula
Market Cap to GDP = (Market capitalisation of all listed companies / GDP of the economy) x 100
A worked example
Illustrative figures, using the workbook's formula and bands. A portfolio manager reviews Indian equity allocation. Total market capitalisation of all listed companies is Rs 280 lakh crore. GDP for the year is Rs 295 lakh crore.
Market cap to GDP = (280 / 295) x 100 = 94.9%
On the workbook's table, 94.9% falls in the 90% to 110% band — moderately overvalued. It is below the 110% overvalued line and above the 90% fairly-valued boundary.
Her client's strategic allocation is 60% equity on a Rs 2 crore portfolio, that is Rs 1,20,00,000. Following the workbook's illustration, she would sell only once the ratio moved beyond 100%, so at 94.9% she makes no tactical reduction yet and simply records the reading.
A year later the market has risen and GDP has grown more slowly. Market capitalisation is Rs 330 lakh crore against GDP of Rs 315 lakh crore:
(330 / 315) x 100 = 104.8% — still moderately overvalued, but now past the 100% action level in the workbook's example. She trims equity by 10 percentage points, moving Rs 20,00,000 out of equity and into debt.
Had the ratio instead fallen to Rs 150 lakh crore over Rs 330 lakh crore = 45.5%, the reading would be undervalued and below the 50% level at which the workbook's illustrative manager adds fresh tactical allocation.
Why NISM asks about it
Chapter 18, section 18.14.3 (Market capitalization versus GDP), sits inside the global active strategy material and is one of the few places in the chapter with a clean numeric table — which makes it heavily examinable.
Expect a computation from a given market capitalisation and GDP, and a band question: at what ratio is a market fairly valued (75% to 90%) or overvalued (more than 110%). The buy-below-50%, sell-above-100% illustration is also commonly tested, as is the fact that the ratio judges a country, not a company.
Common exam traps
- It values a market, not a stock. An overvalued security is diagnosed against the security market line; a market is diagnosed against GDP. Do not mix the tests.
- The bands are a thumb rule and the workbook says so. They are not a SEBI rule or a valuation standard.
- Read the boundaries carefully. 75% to 90% is fairly valued; 90% to 110% is moderately overvalued. A reading of 88% is not overvalued at all.
- The action levels differ from the band edges. The workbook's illustrative manager buys below 50% and sells above 100% — neither number is a band boundary.
- The numerator is all listed companies. Index-based proxies such as the Wilshire 5000 are approximations to that, chosen for breadth.
- A high ratio does not mean a market will fall tomorrow. The claim is about expected relative returns over time, resting on the assumption that price adjusts to value.
Where this is taught
Free preparation for NISM Series XXI-BRelated terms
- Tactical asset allocationDeliberately shifting a portfolio away from its strategic target to exploit conditions in particular markets, with the stated aim of improving risk-adjusted return rather than simply chasing return.
- IndexA statistical indicator that tracks a portfolio of securities representing a market or part of it, expressed as a change from a base value — so the percentage move matters, not the number itself.
- Market capitalizationThe market value of a company: total shares outstanding multiplied by the current market price. It sets index weights and underpins derivatives eligibility and position limits.
- Free-float market capitalisationAn index-weighting method using only the shares actually available to the public — excluding promoter, government and strategic locked-in holdings — so a stock's index weight tracks its tradeable size.
- Fundamental P/EThe P/E ratio implied by the dividend discount model — derived from a firm's payout ratio, required return and expected dividend growth rather than observed from the market price.
- Overvalued securityUnder CAPM, a security whose estimated return plots below the Security Market Line — it is expected to earn less than its systematic risk warrants under market equilibrium.
- Undervalued securityUnder CAPM, a security whose estimated return plots above the Security Market Line — earning more than its systematic risk (beta) warrants under market equilibrium.