Financial market efficiency
There are several concepts of efficiency for a financial market. The most widely discussed is informational or price efficiency, which is a measure of how quickly and completely the price of a single asset reflects available information about the asset's value. Other concepts include functional/operational efficiency, which is inversely related to the costs that investors bear for making transactions, and allocative efficiency, which is a measure of how far a market channels funds from ultimate lenders to ultimate borrowers in such a way that the funds are used in the most productive manner. Market efficiency  types. Three common types of market efficiency are allocative, operational and informational. However, other kinds of market efficiency are also recognised. James Tobin identified four efficiency types that could be present in a financial market: 1. Information arbitrage efficiency Asset prices fully reflect all of the privately available information (the least demanding requirement for efficient market, since arbitrage includes realizable, risk free transactions) Arbitrage involves taking advantage of price similarities of financial instruments between 2 or more markets by trading to generate profits. It involves only risk-free transactions and the information used for trading is obtained at no cost . Therefore, the profit opportunities are not fully exploited, and it can be said that arbitrage is a result of market inefficiency. This reflects the semi-strong efficiency model. 2. Fundamental valuation efficiency Asset prices reflect the expected flows of payments associated with holding the assets (profit forecasts are correct, they attract investors) Fundamental valuation involves lower risks and less profit opportunities. It refers to the accuracy of the predicted return on the investment. Financial markets are characterized by predictability and inconsistent misalignments that force the prices to always deviate from their fundamental valuations. This reflects the weak information efficiency model . 3. Full insurance efficiency This ensures the continuous delivery of goods and services in all contingencies. 4. Functional/Operational efficiency The products and services available at the financial markets are provided for the least cost and are directly useful to the participants. Every financial market will contain a unique mixture of the identified efficiency types. Informational efficiency. Informational efficiency levels. In the 1970s Eugene Fama defined an efficient financial market as ""one in which prices always fully reflect available information”". Fama identified three levels of market efficiency: 1. Weak-form efficiency Prices of the securities instantly and fully reflect all  information of the past prices. This means future price movements cannot be predicted by using past prices, i.e past data on stock prices is of no use in predicting future stock price changes. 2. Semi-strong efficiency Asset prices fully reflect all of the publicly available information. Therefore, only investors with additional inside information could have an advantage in the market. Any price anomalies are quickly found out and the stock market adjusts. 3. Strong-form efficiency Asset prices fully reflect all of the public and inside information available. Therefore, no one can have an advantage in the market  in predicting prices since there is no data that would provide any additional value to the investors. Efficient-market hypothesis (EMH). Fama also created the efficient-market hypothesis (EMH), which states that in any given time, the prices on the market already reflect all known information, and also change fast to reflect new information. Therefore, no one could outperform the market by using the same information that is already available to all investors, except through luck. Random walk theory. Another theory related to the efficient market hypothesis created by Louis Bachelier is the "random walk" theory, which states that prices  in the financial markets evolve randomly. Therefore, identifying trends or patterns of price changes in a market can't be used to predict the future value of financial instruments. Conclusion. Financial market efficiency is an important topic in the world of finance. While most financiers believe the markets are neither efficient in the absolute sense, nor extremely inefficient, many disagree where on the efficiency line the world's markets fall.