Implications of market efficiency

He has also been “criticising for years” the “value-at-risk” (VAR) models used by institutional investors to work out how much capital they need to set aside as insurance against losses on risky assets. These models mistakenly assume that the volatility of asset prices and the correlations between prices are constant, says Mr Scholes. When, say, two types of asset were assumed to be uncorrelated, investors felt able to hold the same capital as a cushion against losses on both, because they would not lose on both at the same time. However, as Mr Scholes discovered at LTCM and as the entire finance industry has now learnt for itself, at times of market stress assets that normally are uncorrelated can suddenly become highly correlated. At that point the capital buffer implied by VAR turns out to be woefully inadequate.

There are three forms of EMH: Weak, Semi-strong and Strong. Here's what each says about the market.

We then look in detail at the March 2015 proposal by FSB-IOSCO for an assessment methodology for the identification of non-bank non-insurance systemically important financial institutions.


What market efficiency does not imply:

Necessary conditions for market efficiency

A certain degree (2-5%?) of central planning is always needed, and this need for control and variety-reduction increases during a crisis, but on average, centrally planned economies are outcompeted by ones that locally self-organize their own laws, markets, and prices via two-way, evolutionary communications.


Investor Home - The Efficient Market Hypothesis

When it comes to the all-too-human problem of recessions and depressions, economists need to abandon the neat but wrong solution of assuming that everyone is rational and markets work perfectly. The vision that emerges as the profession rethinks its foundations may not be all that clear; it certainly won’t be neat; but we can hope that it will have the virtue of being at least partly right.

The Efficient Market Hypothesis states that at any given time, ..

The objective of an exchange traded fund (ETF) is precisely to offer an investment vehicle that presents a very low tracking error compared to its benchmark.

The implications of the efficient market hypothesis are truly ..

So here’s what I think economists have to do. First, they have to face up to the inconvenient reality that financial markets fall far short of perfection, that they are subject to extraordinary delusions and the madness of crowds. Second, they have to admit — and this will be very hard for the people who giggled and whispered over Keynes — that Keynesian economics remains the best framework we have for making sense of recessions and depressions. Third, they’ll have to do their best to incorporate the realities of finance into macroeconomics.

Implications of the Efficient Market Hypothesis for …

There were some exceptions. One line of work, pioneered by none other than Ben Bernanke working with Mark Gertler of New York University, emphasized the way the lack of sufficient collateral can hinder the ability of businesses to raise funds and pursue investment opportunities. A related line of work, largely established by my Princeton colleague Nobuhiro Kiyotaki and John Moore of the London School of Economics, argued that prices of assets such as real estate can suffer self-reinforcing plunges that in turn depress the economy as a whole. But until now the impact of dysfunctional finance hasn’t been at the core even of Keynesian economics. Clearly, that has to change.

The Efficient Market Theory and Evidence: Implications …

Meanwhile, what about macroeconomics? Recent events have pretty decisively refuted the idea that recessions are an optimal response to fluctuations in the rate of technological progress; a more or less Keynesian view is the only plausible game in town. Yet standard New Keynesian models left no room for a crisis like the one we’re having, because those models generally accepted the efficient-market view of the financial sector.