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What is the CAPE ratio?

Do you often find yourself scratching your head, wondering whether a particular stock is overvalued or undervalued? Well, you’re not alone! Many equity investors face this dilemma as they try to make informed investment decisions. Thankfully, various valuation metrics provide clarity on this front. However, most have limitations, making it a challenging task to determine a stock’s true value. Enter the CAPE ratio – an innovative improvement over basic valuation measures. 

In this article, we’ll look in-depth at the workings, uses, and debates around the CAPE ratio. Read on for a nuanced perspective on navigating this intricate but insightful valuation tool.

What is the CAPE ratio?

The CAPE, or Cyclically Adjusted Price-to-Earnings ratio, compares a company’s current share price to its inflation-adjusted average earnings over the past 10 years. The logic is that fluctuations in corporate profits over the economic cycle can skew valuations in the short run. The CAPE ratio smooths out these fluctuations to arrive at a longer-term, normalised metric. 

More specifically, the CAPE ratio is calculated as:

Current Stock Price / Average Annual Inflation-Adjusted Earnings per Share Over Past 10 Years

The CAPE ratio improves upon the traditional P/E ratio by accounting for business cycles and using inflation-adjusted earnings. However, it still comes with imperfections.

The origins and aims of the CAPE ratio

The CAPE ratio was conceptualised in 1988 by Yale economist Robert Shiller, who later won a Nobel Prize for his work on asset valuation. His innovation came amidst the 1987 stock market crash when investors recognised the need for valuation metrics to better indicate overheated markets.

The core objective of the CAPE ratio mirrors that of the simple P/E ratio – to assess whether stocks seem overpriced or underpriced relative to company earnings as a reference point for approximate intrinsic value. However, by considering 10 years of inflation-adjusted earnings, the CAPE ratio aims to provide a more stable, meaningful valuations gauge.

When we talk about the stock market, there is something called the CAPE ratio that helps us understand if the market is expensive or cheap. If the CAPE ratio is high, it can mean that the market is at risk of going down soon. But if the ratio is low, it can mean that there’s a good chance the market will do well in the future. However, experts still need to figure out the exact values of the CAPE ratio that indicate whether the market is overvalued or undervalued.

Potential uses for investors

Investors can employ the cape ratio in a few ways:

1. Gauge market valuations

The CAPE ratio for major indexes like the NIFTY 50 helps investors get a big-picture sense of equity valuations adjusted for the business cycle. Index CAPE ratios substantially above or below historical averages could indicate impending corrections or brighter prospects.

2. Evaluate individual stocks

The CAPE ratio can also be calculated to assess individual companies’ valuation. Comparing a stock’s CAPE ratio to appropriate benchmark averages and sector medians gives more context on stretched or reasonable valuations.

3. Inform asset allocation

Index CAPE ratios meaningfully above or below averages may prompt investors to trim or bolster exposure to equities relative to bonds, cash, etc., based on perceived over/undervaluation. This application links to the metric’s origins in signalling heightened market risk

However, analysing the CAPE ratio is more complex.

Examining criticisms and limits of the metric

While the CAPE ratio improves upon simpler valuation gauges, conceptual and practical concerns still surround it, including:

1. Backward-looking flaws

The CAPE ratio relies exclusively on historical data, making it more logical for assessing past returns than predicting future performance. Markets evolve so that past earnings may have little bearing on forthcoming profits.

2. Accounting changes

Variations in accounting standards and procedures over 10 years can complicate inflation-adjusted earnings averages.

3. Imprecise market correction signals  

Very high CAPE ratios usually indicate overvaluation but don’t pinpoint precise market correction timeframes. Also, markets can remain highly valued or even become further overextended for years before reversing.

4. Sector differences matter

Unique industry traits legitimately justify higher or lower CAPE ratios. Comparing a stable sector to a volatile one using the same CAPE threshold is flawed.

In essence, while the CAPE ratio improves upon simpler P/E metrics, it cannot be viewed as a precise, foolproof predictive gauge. Mindfulness of its nuances is key.

Navigating ongoing expert debate

Given limitations like time lag and accounting inconsistencies over 10 years, even experts debate the metric’s predictive capacity. Divergent opinions on useful CAPE ratio thresholds for signalling over- or under-valuation also abound.

Some strategists argue ratios over 25 indicate elevated risk, while others see ratios up to 45 as reasonable, given today’s low-interest rates. Conversely, while ratios below 15 suggest potential undervaluation, low inflation now may justify lower ratios.

In September 2020, the S&P 500 CAPE ratio hit 30.84, fueling warnings of overvaluation. A year later, it rose further to 38.34, demonstrating how markets can defy risks portended by elevated ratios for extended periods.

Ultimately, precise agreed-upon thresholds are still being determined. While CAPE ratios should inform evaluation, other qualitative factors like growth trajectories and competitive strengths also matter greatly for investment decisions and timing market risk.

Reflection on the metric and provision for investors

The CAPE ratio is a tool used by investors to evaluate the value of stock market indexes and individual stocks. It takes into account fluctuations in the economy over 10 years and adjusts for inflation. 

While the CAPE ratio can help smooth out short-term fluctuations in profits, it has limitations when it comes to predicting market trends in dynamic markets. Using it as a tool in conjunction with other methods to make informed investment decisions is important.

This suggests a nuanced approach for investors leveraging the CAPE ratio:

  • Compare indexes/sectors using consistent benchmarks over time 
  • Assess individual stocks relative to appropriate sector medians
  • View substantially high or low CAPE ratios as a reason for deeper analysis rather than definitive signals
  • Let the CAPE ratio inform evaluation alongside other financial metrics and qualitative insights

When it comes to investing, it is always a good idea to listen to different experts’ opinions. One thing to keep in mind is that it’s only sometimes helpful to rely on strict rules for determining whether a market is overvalued or undervalued because sometimes markets can behave irrationally for longer periods than we might expect.


The CAPE ratio is a tool that can help us understand if the stock prices are reasonable or not by looking at the average earnings of companies over the past ten years. Although it may not be perfect, it can help us see beyond the ups and downs of the market and figure out if stocks are currently overpriced or underpriced. However, it can be complex to analyse stocks in general, so it’s important to keep that in mind.


What exactly is the CAPE ratio, and what does it tell investors?

The CAPE, or Cyclically Adjusted Price-to-Earnings ratio, compares a stock or market index’s current price to average annual earnings over 10 years, adjusted for inflation. It indicates potential overvaluation or undervaluation by smoothing out corporate profit swings over the business cycle. High CAPE ratios suggest possible overheating, while low ratios indicate underpricing.

How is the CAPE ratio calculated, and how does it improve on the P/E ratio?

The CAPE ratio equals the current share price divided by the 10-year average of inflation-adjusted annual earnings per share. Factoring in inflation and longer-term earnings provides a more stable metric than the basic P/E ratio. The P/E can fluctuate widely with corporate profits over short-term economic cycles.

What are some key applications and potential benefits of this ratio for investors?

Investors can use the CAPE ratio to gauge valuations of the overall market, specific sectors, or individual stocks. Comparing CAPE ratios to historical averages provides context on stretched or reasonable valuations. Major market index CAPE ratios also help investors evaluate risks, make asset allocation decisions between stocks and bonds, and find potential value opportunities.

What are some major criticisms, limitations and ongoing debates regarding the CAPE ratio?

Critiques include that backward-looking earnings data has limited predictive ability for future returns. Accounting changes over 10 years also complicate easy comparisons. High CAPE ratios indicate overvaluation but need to pinpoint when markets will correct. Experts have also debated the useful threshold ranges for high/low CAPE ratios. Overall, the CAPE ratio cannot provide foolproof signals; rather, it is one analytical lens among many.

How should equity investors incorporate analysis based on the CAPE ratio?

Investors should avoid rigid over-reliance on specific CAPE thresholds and instead use the ratio as one input for overall assessment. Comparing sectors using consistent standards is useful, as is measuring individual stocks against appropriate industry medians. The CAPE ratio is best utilised to flag possible over- or under-valuation deserving deeper fundamental analysis rather than as a precise predictive signal.

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