The Noisy Market Hypothesis (NMH) is a financial theory that proposes that financial securities prices do not reflect all available information about a company, and market prices are not always efficiently calculated.
This is because the market is subject to noise, or random and irrational fluctuations, caused by the emotions and biases of market participants, dislocations (e.g., lack of liquidity), speculation, momentum, diversification, tax purposes, and other reasons not related to fundamental value.
The NMH is often contrasted with the Efficient Market Hypothesis (EMH), which holds that stock prices reflect all available information about a company and that it is impossible to consistently outperform the market through any kind of analysis or prediction.
While the EMH is often accepted as one view of how financial markets operate, in general – particularly when talking about how difficult it may be to outperform financial markets, or add alpha – the NMH has gained some support as a more realistic description of how markets actually behave, particularly during times of market stress.
Noisy Market Hypothesis vs. Efficient Market Hypothesis
The Noisy Market Hypothesis (NMH) and the Efficient Market Hypothesis (EMH) are two competing theories that seek to explain how prices are determined in financial markets.
The EMH is based on the idea that financial markets are highly efficient, meaning that they accurately reflect all available information at all times.
According to the EMH, prices of securities such as stocks, bonds, and other assets fully reflect all publicly available information, making it very difficult for investors to consistently achieve above-average returns through trading.
In contrast, the NMH acknowledges that financial markets are not perfectly efficient, but instead are affected by “noise” such as misinformation, irrational behavior, and other factors that can cause prices to deviate from their true value.
The NMH suggests that these deviations can be exploited by investors to achieve above-average returns.
Efficient Capital Markets Explained
Noisy Market Hypothesis, Efficient Market Hypothesis, and Trader/Investor Behavior
One key difference between the two hypotheses is their view of the role of investor behavior.
The EMH assumes that investors are rational actors who always act in their own best interests, while the NMH acknowledges that investor behavior can be irrational and influenced by emotional/psychological factors as well as perfectly rational reasons (e.g., hedging, diversifying a portfolio, tax efficiency).
Overall, the debate between the NMH and EMH centers on the degree to which financial markets accurately reflect all available information, and whether it is possible for investors to consistently achieve above-average returns through trading.
Adaptive Market Hypothesis
The Adaptive Market Hypothesis (AMH) is an economic theory that proposes that financial markets evolve and adapt to changing conditions, and that market participants’ behavior and expectations adapt to these changing market conditions.
The AMH suggests that traditional financial models, which assume that markets are efficient and that market participants behave rationally, do not fully capture the complexity of real-world financial markets.
According to the AMH, financial markets are not perfectly efficient, but rather are constantly adapting and evolving (“open systems”) and therefore can’t always discount perfect information.
Market participants do not always behave rationally, but rather adapt their behavior based on their experiences and changing market conditions.
As a result, the AMH suggests that it is not possible to consistently outperform the market by using traditional financial models (because they reflect all that’s known), and that the best approach to investing/trading is to understand (or have an edge on knowing) what others don’t know.
The AMH has been proposed as an alternative to the efficient market hypothesis (EMH), which states that financial markets are efficient and that it is not possible to consistently outperform the market and the less-popular noisy market hypothesis (NMH), which suggests markets get out of whack for various reasons, rational or irrational.
The AMH challenges the EMH by pointing out that financial markets are not always efficient and that market participants do not always behave rationally.
Overall, the AMH provides a more realistic and nuanced view of how financial markets operate, and suggests that traders/investors need to be flexible and adaptable in order to succeed (i.e., add alpha) in the markets.