The Adaptive Markets Hypothesis

In his March 2005 paper entitled “Reconciling Efficient Markets with Behavioral Finance: The Adaptive Markets Hypothesis”, Andrew Lo presents a framework for unifying the Efficient Markets Hypothesis (EMH) and Behavioral Finance. The paper is thoughtful and thought-provoking. Some key points are:

The Adaptive Markets Hypothesis (AMH) is based on principles of evolutionary biology such as competition, mutation, reproduction, and natural selection. It holds that the impact of these forces on market participants determines the level of market efficiency and drives the evolution of the financial industry (survival of the richest), including the rise and fall of institutional and individual fortunes. Behavioral biases are heuristics taken out of evolutionary context. Over time, competitive forces reshape counterproductive heuristics to fit a changing environment. Prices reflect as much information as dictated by the combination of environmental conditions and the number and nature of “species” in the financial ecology. Profit opportunities are the natural resources of this ecology.

The precepts that guide AMH are:

• Individuals act in their own self interest.
• Individuals make mistakes.
• Individuals learn and adapt.
• Competition drives adaptation and innovation.
• Natural selection shapes market ecology.
• Evolution determines market dynamics.

AMH has the following implications:

(1) The equity risk premium varies over time according to the recent stock market environment and the demographics of investors who experienced the environment;

(2) Adaptive asset allocation can exploit the evolution of the market environment, including the systematic changes in the behaviors of its inhabitants;

(3) All investment products experience cycles of superior and inferior performance;

(4) The level of market efficiency varies continuously over time and across markets; and,

(5) Individual and institutional risk preferences also vary over time.

In summary, principles of evolutionary biology such as competition, mutation, reproduction, and natural selection drives the evolution of financial markets.

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