"Money Machines An Interview with an Anonymous Algorithmic Trader"
From Logic Magazine:
In recent years, we’ve been hearing more about the role of
algorithms in our lives. Algorithms are helping decide whether people
get a job or a loan, what news (fake or otherwise) they consume, even
the length of their prison sentence.
But algorithms are
also rewiring the world of finance, with immensely important
consequences. In an era of financialized capitalism, finance plays a
powerful role in the global organization of wealth and work—which means
that everyone will feel the effects of the industry’s transformation.
We
sat down with an algorithmic trader to learn more about how algorithms
are remaking the industry, and why it matters. We talked about what
algorithmic finance actually looks like, who the winners and losers are
likely to be in the new big data gold rush, and why we may be entering
an era of irrational cyborg exuberance.
Let’s start by talking about your background. How did you get involved in finance?
I
was always interested in economics and had a quantitative background.
Anyone who succeeds academically where I grew up ends up being very
quantitatively oriented. After school, as I was trying to find a
profession that would be financially rewarding but would also allow me
to use what I studied, I started looking at the financial industry. I
ended up taking a job on a trading floor in an investment bank.
Most
large banks have at least one, typically several trading floors. It’s
an actual floor, about the size of a football field, filled with traders
who do business with large investors looking to trade stocks, bonds, or
futures, or to borrow money. The bank makes money by taking a
commission, or by “market-making”—intermediating between buyers and
sellers, taking some risk with its own money while it waits for the two
sides to match up.
When I think of a trading floor, I think of a bunch of guys screaming into the phone, Wolf of Wall Street-style.
It’s
not so much people yelling into the phones anymore. The trading floor
has evolved quite a bit over time. It used to be more about being alive
to the transactional flow of global markets. It’s increasingly about the
operations that enable that flow, and the intellectual property that
allows people to make money off that flow.
I liked it. The
trading floor is still where a lot of the actual design and transactions
of global markets take place. And it’s stimulating. If you want to use
your intellectual muscles, you can do so pretty quickly. You’re not just
sitting at a desk somewhere out of the way, or trying to pitch
corporate titans with some arbitrary analysis to back you up —which can
be more of a salesmanship game and less of an intellectual exercise.
Anyway,
over time I migrated to the investment strategy part of the financial
world. I started helping large asset owners—entities like pension funds
and sovereign wealth funds—allocate their money to systematic investment
programs. That’s where I migrated to because that’s where most of the
financial world was migrating to after the 2008 financial crisis, as
everyone realized that the old ways of investing were not really doing
what they wanted them to do.
Portfolios had been too exposed to
the same underlying risks. Technology was now enabling investors to
understand their risks better, and to take more direct control over
their investments. Part of the shift involved removing human
decision-making when it wasn’t perceived as adding any value.
What
do those new ways of investing look like? What are “systematic
investment programs,” and how do they fit into the field of algorithmic
finance as a whole?
There are many ways that
algorithms are actually used in finance, so the term algorithmic finance
gets used more loosely than it should.
There are at least two
major domains in which algorithms dominate. The first is what’s
frequently called algorithmic trading, which focuses on market
microstructures. It programs computers to make split-second automated
decisions on how stocks are bought and sold. Should you buy a whole
bunch of shares at once? Or should you split up your purchases over
time? How do you more intelligently execute trades? Algorithmic trading
uses algorithms to help answer these questions—and it’s an enormous
industry. There are a lot of hedge funds and traditional investment
banks that try to make money there.
The other domain, which is
the one that I’m more focused on, is sometimes called systematic
investing and sometimes called quantitative investing. It’s also very
much algorithmic investing. It involves using algorithms to allocate
money systematically based on data.
An early version of
quantitative investing—starting roughly in the 1950s, with the birth of
Modern Portfolio Theory—was designed to create rules to save for
retirement. These rules were supposed to help people decide how much of
their money to put into stocks and how much of it to put into bonds.
Once you’ve made that decision, you have a rule that lets you allocate
money across stocks and bonds at some defined frequency automatically,
without a human being going in and having to make any qualitative
decision. This basic framework was rapidly adopted across investment
portfolios at every scale, from mutual funds for individual investors to
asset allocation decisions by the largest funds in the world.
Then
people took that framework and applied it to an increasing number of
underlying assets, with a much finer degree of granularity. So now
you’re not just making rules that determine the overall mix of stocks
and bonds in a portfolio but which stocks, which bonds, which
commodities, which corn futures, and so on. And the rules used to
distribute assets become far more complex.
When you say “making rules,” what exactly are we talking about here?
The
simplest rules can be run on a basic spreadsheet. For instance, classic
pension portfolios used to allocate 60% of the portfolio to large-cap
stocks and 40% to bonds. Then Modern Portfolio Theory started to
allocate assets accounting for mathematically measured risk and return.
You run a giant optimization that promotes diversification—across stocks
within your stock portfolio, across asset classes—to maximize the
return you make per unit of risk.
These rules didn’t need
any further human intervention, in the sense that they completely
defined a portfolio. But in practice, investment wasn’t completely
rule-based: investors used the model outputs as a baseline, and then
tweaked it with their own decisions. Human insight could further improve
the asset mix, in a variety of ways. Investors might want to buy
cheaper stocks, for instance, or “time” the market by getting in or out
at the right time. Or they might want to find new assets like
commodities and mortgage securities, or improve the measurement of risk.
More
recently, however, advances in computing power and financial
engineering have vastly expanded the universe of analytical tools that
can be applied to investing. The latest “rules” involve developing
machine learning models that train on large amounts of data. It could be
data from the financial statements of publicly traded companies. It
could be macroeconomic data. It could be the price history of certain
financial instruments. It could also be more esoteric data like
satellite imagery.
What’s a concrete example of an investment decision driven by a machine learning model?
You
could purchase a “sentiment” score developed by a firm that trawls
Twitter on a continuous basis to understand changes in the mood of the
market, or around a specific company. You could use that data to train
your model, which could then determine whether to buy or sell certain
shares. Usually signals like a sentiment score decay pretty quickly
though, so you would want to be able to make that trade fast.
How
automated would that process be? Are we talking about software making
recommendations to human traders, or actually executing trades itself?
The
level of human oversight varies. Among sophisticated quantitative
investors, the process is fairly automatic. The models are being
researched and refined almost constantly, but you would rarely intervene
in the trading decisions of a live model. A number of hedge funds,
mutual funds, and exchange-traded funds (ETFs) run on auto-pilot.
By
contrast, most traditional investors use models to provide guidance
rather than to generate automated trading decisions, since its unlikely
that they could operationalize a complex trading strategy.
One
of the challenges with machine learning is explainability. As the model
becomes more complex, it can become harder, even impossible, to explain
the results that it generates. This has become a source of concern as
public scrutiny of the tech industry has increased, because you have
algorithms making decisions that affect people’s lives in all sorts of
ways while the reasoning for those decisions remains completely opaque.
When
the financial industry plugs a bunch of data into a model in order to
make an investment decision, how important is the explainability of the
result?
I think the result should be very
explainable. But that’s not a universal view. In fact, there’s a fairly
big split between people who have concluded that explainability is
holding back the advancement of the use of these techniques, and the
people who hold on to the rather quaint notion that explainability is
important.
But to some extent, explainability was already an
issue well before we started using machine learning, because even
traditional models of investing were hampered by some of these same
issues. Finance is not like physics. You have a lot of feedback loop
mechanisms impacting how participants interact with financial markets.
To
give you a simple example, you might look at the price data of a stock
and conclude that because that stock went up last month, it’s a good
idea to buy that stock today. And if you do that systematically, you
might expect to make some money. But if everybody else comes to the same
conclusion, then the stock could get overbought today based on the
movement of the stock over the past month. And if it’s overbought, you
might actually expect to lose money on it over the next month.
Looking
at historical data to figure out where your investment is going to go
is useless if you haven’t thought about the mechanism by which it’s
going to do that. In the example I gave, if you didn’t have an
explanation for why the stock was moving the way it was moving,
you might have missed the fact that the underlying mechanism didn’t
really exist, or that it wasn’t robust enough to weather a whole lot of
market participants looking to take advantage of that phenomenon.
So
explainability has been an issue for a while. Everyone is always
looking for a story for why they’re doing what they’re doing. And many
of those stories aren’t that robust.
But isn’t there a strong financial incentive to try to understand why
you’re doing what you’re doing, whether it’s an algorithm or a human
executing the trades? Otherwise it seems very easy to lose a lot of
money.
Sure. But the market structure of investing dilutes that incentive.
The
people who are developing the most sophisticated quantitative
techniques work for hedge funds and investment banks. For them, there
are two ways to make money. You make money by charging fees on the
assets you manage, and you make money on the performance of the fund.
That split will give you a sense of why there’s a dilution of the
incentive. Because even if your assets don’t perform well, you can still
make money on the fees that you’re charging to manage those assets.
The
rewards from those fees are so large that if you can sustain a story
for why your technique is superior, you can manage assets for a long
time and make a ton of money without having to perform well. And, to be
fair, sometimes it takes a number of years before you know whether the
quantitative technique you tried actually works or not. So even if you
aren’t making money in the short term, you could have a reasonable story
for why you aren’t.
At the end of the day, for the manager, it’s
as important to gather a lot of assets as it is to run a successful
strategy. And gathering assets can be largely a marketing game.
And
you play that marketing game by talking about your algorithms and
machine learning models and artificial intelligence techniques and so
on.
That’s right. Let’s look at hedge funds in
particular. Hedge funds are a very expensive form of investment
management. So they need to justify why they’re getting paid as much as
they’re getting paid.
There’s a large amount of data that
suggests that the average hedge fund, after you’ve paid all the fees
that they charge, is not doing much for you as an investor. The last
several years in particular have not been very kind to the hedge fund
industry in terms of the returns they’ve produced. So hedge funds have a
strong incentive for differentiation in their marketing story. The
first marketing question for a hedge fund is always, “Why are you not
the average hedge fund?”
Investors want to know how a
hedge fund is going to make money, given the poor performance of the
hedge fund industry as a whole. These days, investors are excited by an
orientation towards technology and big data and machine learning and
artificial intelligence. These tools offer the promise of untapped
returns, unlike older strategies that may have competed away the returns
they were chasing. Regardless of whether you’re actually good at
technology as a hedge fund, you want to have a story for why you might be.
Some
of the most prominent hedge fund managers of the last few decades—Steve
Cohen, Paul Tudor Jones—are going against type and launching
technology-driven quantitative investment funds. They employ physicists
and computer scientists to write algorithms to invest money, because
that’s what investors want. You’re seeing a massive arms race across
hedge funds to rebrand themselves in that direction.
It
reminds me a bit of startup founders marketing themselves to Silicon
Valley venture capitalists by peppering their pitch decks with buzzwords
related to artificial intelligence or some other hot field. The
startups might get funded, but the technology might not really work—or
it might not even exist. What the startup is calling artificial
intelligence could be a bunch of workers in the Philippines doing manual
data entry....
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