Cyclically Adjusted Price Earnings Ratio

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The cyclically adjusted price-earnings (CAPE) ratio is a valuation measure applied to equity markets. It is designed to provide a clearer view of a company or market’s earnings by smoothing out the impact of economic cycles. The CAPE ratio is an important tool for investors to gauge whether a stock or market is overvalued or undervalued. This article delves into the CAPE ratio, its calculation, its significance in the financial world, its historical performance, and its limitations.

Understanding the CAPE Ratio

The CAPE ratio, also known as the Shiller P/E ratio, was popularized by economist Robert Shiller. It adjusts the traditional price-earnings ratio by accounting for inflation and averaging earnings over a 10-year period.

Calculation of the CAPE Ratio

The CAPE ratio is calculated by dividing the current market price of a stock or index by the average real earnings over the past 10 years, adjusted for inflation.

\[ \text{CAPE Ratio} = \frac{\text{Current Price}}{\text{Average Real Earnings (last 10 years)}} \]

This formula helps smooth out the fluctuations in earnings caused by the economic cycle, providing a more stable and long-term view of a company’s valuation.

Real Earnings Adjustment

To adjust for inflation, historical earnings are converted to current dollars using the Consumer Price Index (CPI). This adjustment ensures that earnings from different periods are comparable.

Comparison to Traditional P/E Ratio

The traditional P/E ratio is calculated by dividing the current price by the earnings of the last 12 months. While the traditional P/E ratio can be affected by short-term earnings volatility, the CAPE ratio mitigates this by averaging earnings over a longer period.

Stability Over Cycles

The CAPE ratio offers more stability over different economic cycles, making it a more reliable indicator for long-term investment decisions compared to the traditional P/E ratio.

Significance of the CAPE Ratio

The CAPE ratio is a valuable tool for assessing market valuations and making informed investment decisions. It provides insights into whether a market or stock is overvalued, undervalued, or fairly valued.

Market Valuation

A high CAPE ratio suggests that the market is overvalued, implying that future returns might be lower. Conversely, a low CAPE ratio indicates that the market is undervalued, suggesting higher future returns.

Historical Benchmarks

Historical benchmarks of the CAPE ratio can provide context for current valuations. For example, a CAPE ratio significantly above the historical average might indicate an overheated market.

Investment Strategy

Investors use the CAPE ratio to guide their investment strategy, including asset allocation and timing decisions.

Long-Term Perspective

By focusing on long-term earnings, the CAPE ratio helps investors maintain a long-term perspective, avoiding short-term market noise and making more informed investment choices.

Risk Management

The CAPE ratio can be a tool for risk management. High CAPE ratios may prompt investors to reduce their exposure to equities, while low CAPE ratios might encourage increased equity investments.

Historical Performance of the CAPE Ratio

The CAPE ratio has been a useful indicator for predicting long-term market performance. Analyzing its historical performance can provide insights into its effectiveness.

Predictive Power

Studies have shown that the CAPE ratio has a strong correlation with future stock market returns. High CAPE ratios have historically been followed by periods of lower returns, while low CAPE ratios have preceded periods of higher returns.

Examples from History

Significant historical examples include the dot-com bubble in the late 1990s, where the CAPE ratio reached extremely high levels, and the subsequent market correction. Similarly, the low CAPE ratios during the financial crisis of 2008 were followed by strong market recoveries.

Over the long term, the CAPE ratio has provided valuable signals for market cycles, helping investors identify periods of overvaluation and undervaluation.

Periodic Adjustments

Periodic adjustments in investment strategy based on the CAPE ratio can enhance long-term portfolio performance by avoiding market extremes.

Limitations of the CAPE Ratio

Despite its usefulness, the CAPE ratio has limitations that investors should consider when using it as part of their investment strategy.

Economic and Market Changes

The CAPE ratio may not fully account for structural changes in the economy and markets.

Changing Market Dynamics

Changes in market dynamics, such as shifts in technology, industry composition, and global economic factors, can impact the CAPE ratio’s effectiveness as a valuation tool.

Interest Rates and Inflation

The CAPE ratio does not directly account for interest rates and inflation, which can influence market valuations and investor behavior.

Time Frame and Data Quality

The 10-year averaging period may not be suitable for all market conditions, and the quality of historical earnings data can affect the accuracy of the CAPE ratio.

Short-Term Anomalies

Short-term market anomalies and unique economic events can distort the CAPE ratio, making it less reliable for short-term investment decisions.

Data Integrity

Ensuring the integrity of historical earnings data is crucial for accurate CAPE ratio calculations. Inconsistent or inaccurate data can lead to misleading conclusions.

Practical Applications of the CAPE Ratio

Investors can apply the CAPE ratio in various practical ways to enhance their investment strategies and decision-making processes.

Asset Allocation

The CAPE ratio can guide asset allocation decisions by indicating the relative attractiveness of different asset classes.

Equity vs. Fixed Income

When the CAPE ratio is high, investors might shift some assets from equities to fixed income to reduce risk. Conversely, a low CAPE ratio might encourage a higher allocation to equities.

Market Timing

While market timing is inherently challenging, the CAPE ratio can provide signals for adjusting investment strategies.

Entry and Exit Points

Investors may use the CAPE ratio to identify potential entry and exit points in the market, enhancing their ability to buy low and sell high.


The CAPE ratio can aid in diversification by highlighting overvalued and undervalued sectors or regions.

Sector Rotation

Investors can use the CAPE ratio to rotate investments into sectors with lower valuations and higher growth potential, optimizing portfolio performance.


The cyclically adjusted price-earnings (CAPE) ratio is a powerful tool for evaluating market valuations and making informed investment decisions. By adjusting for inflation and smoothing out earnings over a 10-year period, the CAPE ratio provides a more stable and long-term perspective compared to traditional valuation measures. While it has proven to be a valuable indicator of future market returns, investors should be aware of its limitations and consider it as part of a broader investment strategy. By leveraging the insights provided by the CAPE ratio, investors can enhance their ability to navigate market cycles and achieve their long-term financial goals.

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