A Trading System that Disproves Efficient Markets

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Efficient market adherents claim it is impossible to outperform the stock market over the long term. Although their principles are the foundation of modern investment theory, other compelling models, including the one I propose here, reveal that precisely the opposite is true, supporting the thesis that markets are highly inefficient.

Challenging the Efficient Market Hypothesis

Dow Theory, an investment philosophy based upon the research of Charles Dow in the late 19th century, contends that the stock market is engaged in a perpetual cycle that moves prices back and forth between undervaluation and overvaluation. According to Dow Theory, secular trends, which typically last from 10 to 20 years, begin when multiples are compressed and gradually drive prices to overvalued extremes, after which the trend reverses and drives them back to undervalued extremes, eliminating the speculative excesses that were introduced by the preceding growth phase. Within secular trends, there are cyclical trends that typically last from two to five years. These also engage in their own smaller cycles, moving higher and lower for several years at a time as the dominant secular current gradually engenders multiple compression or expansion over the course of a decade or more.

Many investors and traders have consistently outperformed the market over the long term, such as Warren Buffett, but in order to effectively prove that markets are inherently inefficient, it is necessary to create a similarly successful, purely mechanical trading system that generates reliable market timing signals based strictly upon the analysis of market data. Such a system needs to analyze a large basket of data, including fundamentals such as valuations, technical indicators such as momentum, market participant sentiment and market internals such as breadth and volume.

In order to be judged successful, the system needs to identify the vast majority of cyclical trend inflection points (i.e., when an investor should get in or out of the market) while generating a minimal number of incorrect signals. Not only is such a system possible, but I have implemented a rule-based software program that has successfully identified 92% of the cyclical trend inflection points from 1940 to 2010 while producing only four incorrect signals.

A mechanical system that identifies market inefficiencies

My system is relatively simple and based upon the fundamental tenet of Dow Theory that claims stock prices are continually moving between areas of undervaluation and overvaluation. While secular trends engender multiple expansion and compression during the course of decades, their component cyclical trends do so on a smaller scale over the course of two to five years. Therefore, the goal of the system is to identify these cyclical valuation extremes, along with the market behavior that suggests the trend is in the process of reversing.

In order to evaluate cyclical trends, my system produces a Cyclical Trend Score (CTS) that provides a quantitative measure of bullishness or bearishness. Generated scores range from -100 to +100; where a reading near 100 indicates the likely presence of a cyclical low, while a reading near -100 suggests the development of a cyclical peak.

The CTS is a composite of scores that analyze specific market characteristics such as valuation, momentum, sentiment and internals. I will review the use of each of these data to demonstrate how they assist in the identification of highly probable cyclical trend inflection points.

The valuation component score

The valuation component score identifies areas of cyclical overvaluation and undervaluation relative to the core valuation of the dominant secular trend. Since secular trends gradually expand and compress multiples over long periods of time, the notions of overvaluation and undervaluation from a cyclical perspective are relative and depend upon the current state of the secular trend.

For example, coming out of the terminal phase of a secular bear market, market multiples are typically in the single digits, so an initial cyclical advance that expands valuations into the teens could easily result in an overvalued condition. Cyclical rallies in mature secular bull markets, however, may need to drive multiples well above 20 before an overvalued state is achieved. The core valuation for the secular environment can be approximated with a simple moving average, after which any number of standard mathematical tools, such as a Gaussian distribution, can be employed to identify cyclical valuation extremes, providing the basis for calculating the cyclical valuation score. The valuation score generated by my program is displayed below during the early stage of the secular bull market that began in 1982.

Valuatio Score