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Chapter 17: Considering a Trading System
Super systems
Algorithmic trading is the fusion of technical
analysis with efficient order entry, and banks
and fund managers initially used this method
to get an advantage in execution speed. One
subset consists of “high-frequency” traders
whose machines can place trades at literally
the speed of light (or just under it), whereas the
human trader may take as long as five or ten
seconds to make a trading decision after the
release of news or the appearance of a trading
opportunity.
Information input needs to be as fast as output
(the trade orders). Data and news vendors, for
a special price, make information available to
big institutions fractionally faster than to the
general public, too. The innate fairness of this
fact is under question today. Algo trading may
account for as much as 75 percent of all securi-
ties trading in the U.S. Does this mean the trad-
ing game is rigged against the little guy? If you
want to do lightning-fast arbitrage, yes. If you
are trend-following, maybe not. You can find
any number of equally valid ways to trade the
same security.
The same problems arise in algo trading as in
any system. Computer programming is deeply
specific. If the program fails to include every
contingency, it doesn’t have a brain that auto-
matically falls back to some kind of default
mode. Data errors caused a “flash crash” in
May 2010, when the Dow fell 998 in under an
hour and some $40 stocks were priced at $1.
Experts doubt that this type of occurrence due
to data error is the last.
When a trade goes bad in some unprecedented
way, humans have a fallback — they exit. But
computers don’t watch TV or read newspa-
pers, so if the trade goes bad, it may have no
programmed instructions on what to do until
after the event starts being reflected in prices.
Markets are notoriously slow to respond to
event shocks. This is one time the human is
faster.
The idea of automating trading is not innately
wrong. After all, the equivalent of robots can fly
an airplane and even land it. But the mechani-
cal and electronic contingency planning under-
lying avionics is vast and has taken decades,
and superlative as it is, would still not be able
to land a very large plane on the Hudson River
after a bird strike. At a guess, engineers are
working on it.
Algo trading is newer and presumably less far
advanced than avionics, although the big insti-
tutions aren’t disclosing information on their
top-secret systems. We can draw inferences,
though. First, big institutions have made big
investments in algo trading that are deliver-
ing a big payoff. In theory, you could duplicate
the effort in every way except high-frequency
trading (unless you’re willing also to pay for
advance information) and market making —
offering a two-way price to any comer for any
size trade.
The second deduction is that vendors of auto-
mated systems or robots have almost certainly
not put hundreds of million of dollars into the
design. If they had, they wouldn’t be promot-
ing it to you for $500 or $5,000. It would literally
be worth more than that. If the system were a
fabulous design, they would sell it to a big insti-
tution for millions. A third flaw in retail-level
systems and robots is that the designer has
embedded into it his own trading philosophy,
by which I mean choice of indicators and risk
appetite. Risk appetite is deeply personal, as I
discuss in Chapter 16. The robot designer may
be willing to lose, say, $3 in an $8 initial buy
whereas your stop would be half that, or $1.50.
Buying somebody else’s system is always going
to disappoint.