Tag Archives: MIT Sloan

What is the optimal trading frequency in financial markets?

Trading speeds in financial markets have increased dramatically over the last decade. In markets for equities, futures and foreign exchange, transactions take place in milliseconds to microseconds (or even nanoseconds). Markets for fixed-income securities like corporate bonds and over-the-counter derivatives like interest rate swaps and CDS are also catching up quickly by adopting electronic trading.

The dramatic speed-up of financial transactions can perhaps only be matched by the intensity of the events and debates surrounding it, especially in the context of high-frequency trading. To many, the Flash Crash of May 2010 was a wakeup call for reevaluating market structure. A series of technology glitches proved to be highly costly for some brokers, proprietary firms and marketplaces in terms of profits and reputation. The SEC launched investigations into HFT firms and their strategies. The French regulators introduced financial transaction tax. Michael Lewis wrote “Flash Boys.” The list goes on.

With these events and controversy come important economic questions: What are the costs and benefits to investors for speeding up trading? Is there an “optimal” trading frequency at which the financial market should operate? And does a faster market affect one group of investors more than another?

In a recent research paper, Welfare and Optimal Trading Frequency in Dynamic Double Auctions, my coauthor Prof. Songzi Du (Simon Fraser University) and I attempt to answer these questions.

Our starting point is very simple. Trading frequency can be measured by how often investors transact through market. A higher-frequency market allows investors to access the market more often per unit of clock time. When investors meet each other in the market, they trade. Trading can be motivated by new information about future asset value and idiosyncratic trading incentives such as tax or inventory considerations.

A fundamental function of financial market is to reallocate assets from investors who value them less to investors who value the assets more, at the right price. The better this function is fulfilled, the more efficient the market is in reallocating the asset. We say that the market “improve welfare”—that is, make all investors better off—if it makes the reallocation of assets more efficient.

The bright side and dark side of a higher-frequency market

A higher trading frequency is double-edged sword. The optimal trading frequency depends on how the benefit and cost balance each other.

On the bright side, a higher-frequency market is more responsive to new information. Investors benefit from being able to react immediately to news. For example, following earnings announcements or merger-acquisition news, an investor may find his previous allocation on a stock no longer desirable. The sooner investors react to this information by trading, the better off they are. This effect favors a high-frequency market.

On the dark side, a higher-frequency market reduces the aggressiveness of investors’ trades. Investors are said to be more aggressive if they are willing to tolerate a greater market impact to achieve their target asset position. For example, aggressive execution means trading larger quantities more quickly. By contrast, unaggressive execution means splitting a large order into many small pieces and trading them gradually over time. The more frequently the market allows investors to transact, the stronger is their incentive to split orders over time to avoid price impact; hence, it takes longer to reach desired asset positions, and this is inefficient. If, however, a market opens infrequently, it encourages investors to trade aggressively now—failing to trade now means waiting for longer for the next opportunity to trade; this in turn leads to a faster convergence to efficient allocations. In this sense, somewhat counter intuitively, a lower-frequency market enhances allocation efficiency.

Scheduled versus stochastic news

We show that the optimal trading frequency depends on the nature of information arrivals, which determines the tradeoff between the benefit and cost of a higher trading frequency.

For scheduled arrivals of information, such as earnings announcements and macroeconomic data releases, we find that the optimal trading frequency should be equal to or lower than the frequency of information arrivals. For example, if news only arrives once per day, it is never optimal for investors to trade more than once a day. Moreover, if the market is competitive enough, the optimal trading frequency is equal to the information frequency.

For stochastic arrivals of information, such as surprise news of mergers and acquisitions, we show that the optimal trading frequency can be much higher. Moreover, if the market is competitive enough, continuous trading (the highest-frequency market) turns out to be optimal.

What does this tell us about optimal trading frequency in reality? Assets such as large-cap stocks or Treasuries that have frequent, unpredictable news shocks should be traded close to continuously. Small, illiquid stocks or bonds that have scarce news may best trade in a low-frequency market that only opens a few times a day; concentrating trading interests at specific time creates a deeper market. Therefore, there is no “one size fits all” optimal trading frequency for all securities.

For more details of this research, see “Welfare and Optimal Trading Frequency in Dynamic Double Auctions”, by Songzi Du and Haoxiang Zhu, http://ssrn.com/abstract=2040609.

Haoxiang Zhu is an Assistant Professor of Finance at MIT Sloan School of Management.

Is Bitcoin a viable currency?

The media and blogosphere have been full of Bitcoin discussions recently and almost everyone has an opinion, but most of these opinions are tied to the technology of Bitcoin, that is, whether this new currency represents a major technological revolution in money.  So, most commentary has focused on questions about Bitcoin’s technological advantages: Is it really secure?  Is it truly anonymous?  Can it be counterfeited?  Are transaction costs actually lower?   Here, here and here are a few of examples and they contain comments like “Bitcoin is the first practical solution to a longstanding problem in computer science called the Byzantine Generals Problem.”  That is, they focus on the technology of Bitcoin.

But what of the finance and economics of Bitcoin?  Does it have the economic properties to be a viable currency?  I don’t think so.

Good money had three economic properties and uses.  It is a unit of account, used to measure and write contracts for things like income, wealth, and prices of goods.  It is a means of payment, used to avoid barter.  And it is a store of value, held to be able to make transactions in the future.  Of these three properties the third is the most important.  Unless money has a stable value, it does not serve the purposes that it should.  People will be wary of accepting something that might lose lots of value, and something with a volatile price makes a bad unit of account.

And my argument is not just that Bitcoin has had wild fluctuations in value that undermine its role as a viable currency, but deeper, that Bitcoin is destined to have wild fluctuations – it is poorly designed and conceived and so is likely to fail as a currency.  Why?

First, and primarily, Bitcoin lacks a mechanism for setting the supply of Bitcoin equal to the demand for Bitcoin to maintain its value.  History is replete with examples of governments that tied their hands in the supply of their currencies, much like Bitcoin has done.  What happens?  The value of the currency fluctuates.  Often a lot.  Before the founding of the Fed in the US, the dollar was backed by gold, and gold discoveries lead to inflations, and collapses in the price of gold to recessions and even financial crises.  Since the end of the Great Depression in the US, the Fed has actively managed the money supply to achieve price stability (at some times better than others).

Consider the example of the Y2K scare.  Before January 1, 2000, people were concerned that the change from the year 1999 to the year 2000 could lead to serious errors in computer systems, and in particular that it might become hard to use credit cards or get money out of a bank (or worse, bank deposits might even get lost).  As a result, people withdrew cash before New Year’s, lots of it. (These types of cautionary actions were widespread: governments grounded all airline flights overnight.).  These withdrawals were increased demand for cash that might have driven up the price of dollars – ie. led to deflation and changed interest rates.  But the large increase in the demand for cash did not cause any such real economic effects.  Why?  Because when demand increased the Fed simply expanded the amount of currency in circulation.  When New Year’s came and went without serious incident, people re-deposited their cash and the Fed reduced the money supply. The US price level remained stable.

Similar examples abound.  Prior to the founding of the Fed, the seasonal agricultural cycle lead to big seasonal swings in the demand for credit and currency which lead to seasonal swings in nominal interest rates (that is, the usual interest rate we think of which is the real interest rates plus changes in the value of money, that is, plus inflation).  If Bitcoin gains traction, will it have a seasonal fluctuations in its value that track the seasonal spending patterns of the world.  Will Bitcoins be more valuable in early December and comparably cheap in January?

Every day, central banks supply their currencies in proportion to the needs of the users of their currencies, so as to maintain a stable value for their currencies.  Bitcoin does not have a central bank.  It has a relatively inflexible supply mechanism (known as Bitcoin mining).  As a result, Bitcoin is destined not to have a stable value.  And a volatile price is bad for Bitcoin’s usefulness as a currency.  Central banks are an enormous competitive advantage for traditional currencies that the Bitcoin supply process completely lacks.

A second problem with maintaining a stable value is that digital currency is not really in limited supply. Its proponents will argue that it is.  The Bitcoin technology is carefully, maybe even brilliantly, designed to ensure that the supply grows slowly and it ultimately limited. But what happens when Bitcoin 2.0 comes out?  What if it has slightly better properties than the old technology?  Do people stop using Bitcoin 1.0 entirely leading it to become worthless?  Probably.  Is such a scenario likely?  Well,  think about the potential profits that one could make introducing Bitcoin 2.0, just by keeping a share of the initial number of coins.  These potential profits provide an incentive for the hi-tech business that comes up with a better Bitcoin to take over the digital currency market through advertising, lobbying, payments to businesses and so forth.  Or consider this alternative scenario.  Global banks start to provide currency transfers within their institutions but across borders that are as safe rapid, and low cost as Bitcoin payments.  There is no technological advantage to Bitcoin relative to a global bank with branches in many countries.  The point: while Bitcoin is in limited supply, digital currencies are not and neither are inexpensive ways to transfer money and make payments.

There are several other important cards stacked against Bitcoin.  But I will conclude with only one more., The “money supply” in the every country in the world is actually hard currency times the money multiplier – the ramping up of the hard currency into deposits in banks and lines of credit and gift cards and so forth.  In the US, the money supply – counting all of these money-like assets – is about twenty times the supply of hard currency.  And Bitcoin banking is developing and could go one of two ways.  First, it could be significantly private and unregulated.  The history of unregulated banking is that it is a disaster full of bank runs, volatile price levels currency collapses and so on.  The banking sector’s volatility becomes the volatility of the supply of Bitcoins which becomes price volatility.  Look just recently how the collapse of a single Bitcoin exchange affected the price of Bitcoins.  The second way Bitcoin banking could go would be as a regulated banking sector, becoming part of the tradition banking sector.  But then several claimed benefits of Bitcoin go out the window.  The true, large supply of Bitcoin is governed by banking regulation (but in every country in the world – what a mess!).  And while a Bitcoin is anonymous, a Bitcoin deposit is not anonymous. Once a bank gives you a credit for a Bitcoin and knows who you are, can it see in the Bitcoin chain how it was spent?  Not sure, but I would worry about it.

In sum, I am not worried about the technology – I have complete confidence that people at the other end of the MIT campus can solve almost all of the technological problems.  But the finance is suspect.  I am guessing that Bitcoin either remains small and volatile, with only transactions of suspect legality willing to accept the volatility as the price of true anonymity, or that Bitcoin goes down in history as a bubble, ultimately as worthless as the sequence of zeroes and ones that make up each coin.

MIT Sloan community in NYC gathers for Finance Day

“Pioneers of finance” present research to alumni, students

M2012 Finance DayIT Sloan’s top finance faculty shared new research and led engaging discussions April 20 in New York City, when the School welcomed more than 300 alumni and current and incoming students to its first Finance Day.

At the event, faculty discussed MIT Sloan’s commitment to train the new generation of finance professionals, its role in policy analysis, and the School’s growing finance course and degree offerings, including a new Master of Finance (M.Fin.) program, a complement to the already successful MBA Finance Track.

“We intend to capitalize not just on the MIT finance tradition, but on the MIT tradition broadly defined,” said Andrew Lo, Charles E. and Susan T. Harris Professor of Finance, noting MIT’s leading work in economics, mathematics, operations research, and other fields. Earlier this month Lo was named one of TIME Magazine’s 100 Most Influential People in the World for his theory of adaptive markets and his work developing the federal Office of Financial Research.

Lo called MIT Sloan home to “pioneers of finance,” including Robert Merton, School of Management Distinguished Professor of Finance, Stewart Myers, Robert C. Merton (1970) Professor of Financial Economics, and Stephen Ross, Franco Modigliani Professor of Financial Economics. Myers emceed Finance Day, while Merton and Ross presented research on credit risk and market prediction, respectively. Merton received the Nobel Memorial Prize in Economics in 1997 for developing a new method to determine the value of derivatives.

“Every day there are new insights that these pioneers provide to us,” Lo said. “The M.Fin. program is meant to take that Sloan finance franchise and expand it in a very significant way.”

“Our view is that while there may have been a number of problems in the financial industry—finance itself is not the problem,” Lo said. “In fact, it will ultimately have to be the solution.”

Other presentations at Finance Day included an exploration of how economic booms and busts shape the career paths of CEOs, from Professor Antoinette Schoar, Michael M. Koerner (1949) Professor on Entrepreneurship, and a panel discussion on financial reform featuring Ricardo Caballero, Ford International Professor of Economics at MIT, Blackrock co-founder and chief risk officer Bennett Golub, SB ’78, SM ’82, Ph.D. ’84, U.S. Commodity Futures Trading Commission chief economist Andrei Kirilenko, and Deborah Lucas, MIT Sloan Distinguished Professor of Finance.

MIT and MIT Sloan have an influential history in finance, led by groundbreaking work from Nobel prize-winning economists and other living legends on the faculty. In addition to the Finance Track in the MBA program and a doctoral offering, the School in 2009 launched the intensive one-year Master of Finance.

The financial collapse of 2008 exposed a dearth of properly trained economists working in the financial industry and has led to a policy and regulation quandary that calls for the input of the highly trained financial professionals MIT Sloan creates. The number of MIT Sloan graduates entering the financial sector has been on the rise since 2009.

“We’re growing,” Myers told the crowd, which engaged in a series of insightful question and answer sessions with faculty throughout the day. “The full-time faculty is 18 instead of single digits years ago. We’re now offering 33 different finance courses at MIT, instead of probably single digits year ago.”

Myers urged the alumni at Finance Day to sponsor and encourage colleagues to apply to MIT Sloan’s finance programs, consider hiring graduates, and otherwise be a part of the School’s extensive and influential network of experts and leaders throughout the financial industry.

“As this illustrates,” Myers said, “we’re also reaching out to alumni, friends, and practitioners, anyone who has an interest in finance and is willing to listen to us and talk to us.”