
Why Do High-Frequency Traders Cancel So Many Orders? - yummyfajitas
http://www.bloombergview.com/articles/2015-10-08/why-do-high-frequency-traders-cancel-so-many-orders-
======
chollida1
I think to understand most HFT market makers you have to understand how the
markets pay.

Most work on a maker taker model. Which means the trader who initiates the
trade pays a small fee and the trader who is the passive side, the one who had
their order in the market already, gets paid a small fee. as a side note there
are inverted markets but lets leave those aside for now.

This means to get paid you want to be at the top of the book, which means you
are the first order to get filled when someone crosses the spread to get their
order filled. the way priority is determined is first by price and second by
time. So you have a very vested interest in being the first to cancel and move
your order to the newest price level.

Exchanges have tried introducing some order types to alleviate this constant
send/cancel routine such as the order type "Hide not Slide" but people tend to
get upset at these order types.

Once you understand this, you start to realize that almost all HFT firms
aren't quote stuffing, they are just jockeying for position at the top of the
order book.

I've never really understood quote stuffing, the same firm that quote stuffs
still has to deal with those quotes coming back, its not like the market data
has a flag saying ignore this quote change as its caused by your own quote
stuffing.

The way most markets are setup is that quotes come from gateways and multiple
symbols all share a single gateway, usually assigned alphabetically, so A-F
tickers all share the same gateway. This means that if someone is actually
slowing down market data for say AAPL then they are also slowing down quotes
for AMZN as well but again, the same firm that is quote stuffing also has to
deal with their own mess so I can't see the benefit.

Another comment complains that HFT firms don't like the fragmented market.
That is true to a point, but keep in mind most HFT strategies only work due to
the fragmented markets and RegNMS. So while they may not like 11 venues, they
certainly want atleast 3 or 4, and many of hte top HFT firms run their own
dark pools, adding to the problem:)

As far as Hillary Clinton introducing legislation to curb HFT trading, she was
the senator for New York. I'm dubious of her coming down hard on Wall Street.

~~~
blazespin
Hillary will come down on the part of the market that hasn't contributed to
her campaigns. Structurally, this means she will make it good for GS who will
help write the legislation but bad for anyone else that doesn't belong to the
financial hegemony.

Politicians say they're protecting the innocent, but really they're just
tipping the scales for whoever is backing them. This is how they do.

~~~
arbitrage
What you are describing is not reality.

~~~
jsprogrammer
What do you mean?

GS can already bend the FBI and NY State to their will:
[https://en.wikipedia.org/wiki/Sergey_Aleynikov](https://en.wikipedia.org/wiki/Sergey_Aleynikov)

------
mkinitcpio
Disclaimer: I work in HFT

The article uses the term "front-running" incorrectly. Front-running is where
a firm places their own trades ahead of trades they're placing for a client,
to capitalize on the price movement that client order might generate. This is
illegal.

What the market makers in the article are doing isn't front-running. It's just
being smart with their orders.

And that's generally why HFTs cancel orders- they're reacting to market
conditions that exist on the span of microseconds and will want to change
their market positions very quickly- including canceling orders that they no
longer think are suitable.

~~~
okegoge
It's worth remembering that HFTs like yourself define front-running
differently than others.

Others often (rightfully) feel that HFTs who engage in latency arbitrage where
they take advantage that everyone else is using the NBBO (because they have
to), and the NBBO is lagged, are front-running assholes who extract value
without creating anything.

And we refer to that thieving, predatory, value-stealing activity as 'front-
running', even though technically you're engaging in a slightly different
activity.

~~~
vegabook
I hope you understand that the thievery has been happening for centuries,
millennia. There is no other way to gauge _real_ supply and demand than to put
buy and sell orders into the market yourself. HFT is doing at ultra-high speed
what human market makers do all day long, and have been doing forever.

Now, possibly rightly, market makers in general, through the ages, have had a
bad rap. They are indeed trying to get more information than the average joe,
with very clever, and risky, techniques (see below) and skimming him after
having done so. Nevertheless, you must remember, that without these
people/machines taking these risks, you would not have a continuous market in
which to trade. You'd have a much more stepwise price action and much more
risk. They're providing s service.

Perhaps most controversially, being a good market maker means having some
capital, so that you can wear a loss which is entirely possible during your
price discovery. Thus, market makers who make money, inevitably already have
money. This doesn't help their cause.

But the idea that HFT per se is the problem is wrong. If you don't like HFT,
you don't like finance, period. That may be a legitimate view, or not, but the
two are inextricable. They are not different one from the other - HFT is
simply Amazon doing what Barnes and Noble does, more efficiently (without the
monopoly aspects - HFT is _fiercely_ competitive).

Without HFT, bid offers would be wider. Fact.

~~~
droffel
I agree. I've always thought of HFT as a way to let liquidity flow between
exchanges, with a payoff equal to the degree to which the inter-exchange
spread has been decreased. If the inter-exchange spread is wide, there is some
value to be extracted from that spread, and HFT provides the (in my opinion)
valuable service of extracting that value, making the market more efficient as
a whole. The more people that are competing in that market, the smaller the
value the HFTs can extract, until the actual market participants on the
exchanges are only paying fractions of a penny for the privilege of buying
shares "originating" from another market that has higher liquidity. I can't
really see how this could be a bad thing (given enough competition).

~~~
ConfuciusSay
Well, here's the NY Fed explaining why they think it's bad:

[http://libertystreeteconomics.newyorkfed.org/2015/10/the-
liq...](http://libertystreeteconomics.newyorkfed.org/2015/10/the-liquidity-
mirage-.html#.VhgmFvnnuUm)

------
gbhn
Something this article ignores, and which is ignored by most articles on HFT,
is that the process is ilegible to the public. "No no we're doing you a
favor!" is not reassuring when the activity consumes a bunch of resources on
zero sum activity.

Ultimately investing runs on trust. HFT is consuming public trust in the
financial system at a prodigious rate. Is it a trillion dollars a year? A
billion? Hard to be sure. But it certainly isn't clear the tiny market-making
improvements are worth it.

~~~
kasey_junk
> when the activity consumes a bunch of resources on zero sum activity

The thing to remember about the markets is that each individual trade is
always zero sum, but the value of the markets comes from the aggregate total.

The behaviors that we _want_ in our markets, price discovery, liquidity, easy
risk management are all outcomes that are enabled by speculative market
participants like market makers engaging in lots of zero sum activity.

So instead of decrying the zero sum activity what we want to do is drive down
the price of it to the non zero sum participants. And HFT market making has
been prodigiously good at that.

~~~
Retric
Trading is not a zero sum activity, trades happen because each side want what
the other person has more than what they have which is a net positive. aka I
want lunch more than money.

HFT trading is zero sum because the traders don't actually want or keep stock.

~~~
kasey_junk
No one wants actual stock. They want to gain money on price differences in
stock, or get the dividends that owning stock gives rights to, or I suppose
they want to be able to have the voting rights stocks grant.

The difference is all about timing. I may want something else more than you do
but am willing to sell now. If at the time you close out your trade (that is
sell the shares from me) the price may have risen or fallen. If it rose you
won and I lost by not holding longer.

This time mitigation is precisely what market makers have always done and what
HFT market makers have driven the profits (and thus the costs to outside
participants) out of.

~~~
Retric
Buying stock is trading future money than money today which is a real and
meaningful trade. On the other side, I might want a new car, which means I
want money, which means I want to sell stock.

Even stock to stock transitions can be meaningful as Bill Gates had a lot of
MS stock and wanted a hedge so he sold stock. What he got was probably worth
'less' the diversification was valuable to him making the transaction a net
positive.

~~~
kasey_junk
What you are talking about are precisely the aggregate benefits to the markets
I mentioned, liquidity and easy risk management.

That the markets provide those behaviors is what makes them valuable but the
actual trades that make up those aggregates, your selling of shares when you
need a car to someone else is zero sum. Either you would make more by holding
or you wouldn't.

That something other than that is more important to you indicates that you are
in the market for a middle man to bridge that time gap and buy some of the
risk from you. Your time horizon is from share purchase to "need money for
car", not from share purchase to "optimal selling point". The service you take
advantage of when you bridge that gap is provided by the aggregate work of
many zero sum interactions between speculative participants like market makers
and "investors" like your self.

~~~
Retric
Continuing from the perspective of buying a car:

If I put a sell order on the market at 12:00 the only impact is the sales
price. If it executes at 1PM or 2PM it makes zero difference to me as I can
only access money at the end of the day. So, I only gain liquidity if I would
have been otherwise unable to sell by the end of the day. Therefore, I don't
gain liquidity from HFT.

~~~
yummyfajitas
If you don't want liquidity don't buy it. No one is forcing you.

[https://www.chrisstucchio.com/blog/2014/how_to_not_get_rippe...](https://www.chrisstucchio.com/blog/2014/how_to_not_get_ripped_off_by_hft.html)

------
elecengin
This article brings up something that HF traders have been bemoaning for a
long time: the fragmented US market structure. In US equities, you need to
monitor almost a dozen exchanges to be competitive. The popular book "Flash
Boys" gave the impression that HF traders loved this market structure and used
it to extract more money out of the market. In the majority of cases, this is
wrong.

In fact, the fragmented market results in huge costs (4 datacenters worth of
infrastructure, low latency connectivity, etc) In reality, most market makers
would vastly prefer to simplify this away. This is one of the reasons many
traders have moved to alternative markets that have fewer trading venues (for
example, many futures and options trade primarily on a single venue)

~~~
kevin_thibedeau
The HFT guys love the fragmentation. If not they wouldn't be building out
private microwave links between Chicago and NY to "beat the market".

~~~
minimax
The NY/Chicago arb trade is futures vs equities. In other words it's two
separate products with highly correlated prices. On one side are the futures
contracts and on the other side are the underlying stocks (and ETFs). As long
as the two separate products exist, you'll always have fast arbitrageurs. This
is true whether the matching engines are 1000 miles apart or in the same rack.

------
HiLo
John Arnold (former Enron energy trader) also posted something on Bloomberg
View, and the main gist of the article was:

Front-running is profitable against traditional orders entered by humans. But
with spoofers in the mix, the picture looks quite different: When the front-
running HFT algorithm jumps ahead of a spoof order, the front-runner gets
fooled and loses money. The HFT’s front-running algorithm can't easily
distinguish between legitimate orders and spoofs. Suddenly the front-runner
faces real market risk and makes the rational choice to do less front-running.
In short, spoofing poses the risk of making front-running unprofitable.
Because spoofing is only profitable if front-running exists, allowing both
would ensure that neither is widespread.

[http://www.bloombergview.com/articles/2015-01-23/high-
freque...](http://www.bloombergview.com/articles/2015-01-23/high-frequency-
trading-spoofers-and-front-running)

~~~
zeeshanm
That's why most of these HFT-sponsored exchanges (read: BATS, CHX, etc) pay
retail brokers (e.g. eTrade, Scottrade, etc.) for their flow.

~~~
neomantra
I would be interested in your source for that comment, as I think it is untrue
(at least for US exchanges, I don't know rules in other countries).

I am not saying payment-for-order-flow doesn't exist, but the buyers are firms
like Citadel and other "internalizers", not exchanges.

If by "paying" you are referring to the maker/taker rebate model, that is paid
to any market participant, not just retail brokers.

~~~
elecengin
[https://www.nyse.com/publicdocs/nyse/markets/liquidity-
progr...](https://www.nyse.com/publicdocs/nyse/markets/liquidity-
programs/arca_rlp_fact_sheet.pdf)

[http://cdn.batstrading.com/resources/release_notes/2012/BATS...](http://cdn.batstrading.com/resources/release_notes/2012/BATS-
Introduces-Retail-Price-Improvement-Program.pdf)

~~~
zeeshanm
And these exchanges have historically been doing it. BATS has been around for
about 10 years. But the initial players like Island ECN, Archipelago, and
others (now merged into NSQD, NYSE, etc.) have been paying retail brokers for
their flow since late 90s. This is what attracts big fishes to trade at their
venues.

When you do the wrong over several times without getting caught it becomes a
standard (read: make-or-take rebates)

------
patio11
I happen to have 144 lines of Ruby which implement the world's most braindead
market making algorithm, coded by someone who had literally never written a
trading system before. It cancels ~98% of orders before they are hit when
running on a single stock on a single venue.

~~~
ycombobreaker
Is it profitable? Or just paper trading/simulated? Braindead stuff works if it
is the fastest in the world, but as you slow down you need to get smarter to
cover losses due to getting "picked off" more frequently.

~~~
JoachimSchipper
I'm pretty sure it's a competitor for Patrick's StarFighter game. It's not
supposed to be impossible to beat.

------
sjbase
The "new" part of this news, which not many have responded to here, is the
notion of an HFT tax. The arguments on either side of HFT
(liquidity/spread/etc. vs. cost/unfairness/etc.) have been largely unchanged
for the last few years. There simply isn't enough data made public to declare
a victor.

As far as the tax: personally I'm very in favor of slowing down trading...
unfortunately, what's being proposed introduces as much structural game theory
as it eliminates. What's the dominant strategy for a trader faced with a rule
like "any trades resting for less than 300 micros get taxed"? To be as fast as
possible without triggering the tax; staying just above the threshold.

All that economic waste on low-latency tech will just be redirected to low-
jitter tech. Those who can reliably land an order within +1 microsecond of the
tax line will outperform those who only have an accuracy of +10.

I'd like to see more exchanges experimenting with things like random variance
in speed bump size, frequent batch auctions, etc.

~~~
Mikeb85
> personally I'm very in favor of slowing down trading...

As a retail trader, no.

As an example, yesterday I placed a sell order on $90,000HK worth of a stock.
Once I hit 'send', my order was fulfilled before my browser could load the
confirmation page, and at the market price I was quoted seconds before.

This is, in large part, thanks to market makers who use HFT. Before this, the
broker/market maker might take a spread worth half a percent or more (and
being a retail investor, you probably wouldn't get the 'market' price), now
it's pennies or less, and at the market price.

Thanks to HFT, spreads are smaller, execution quicker, and it definitely
'levels' the playing field.

~~~
sjbase
I completely agree that liquidity is first and foremost, and that in today's
market structure HFT drives a lot of it. Retail enjoys a lot of the benefit,
because trades in the $1,000s - $100,000s range probably aren't enough to slip
the market. But is ultra-low-latency the ONLY way to bring about that
liquidity? I have yet to come across any economic or technical reason why that
has to be the case.

Also, slowing down trading doesn't mean eliminating HFT, it's a matter of what
constitutes "high" frequency... I'd argue we're well past the point where
incremental increases in speed result in equal gains in liquidity. And those
increments now cost more than ever before.

~~~
Mikeb85
When incremental gains are no longer worthwhile, institutions will no longer
invest in the infrastructure. As long as the profit gained > costs, they will
invest in infrastructure, to the benefit of the tech industry.

And you're right, we don't need market makers trading as fast or as frequently
as they do, but they see an opportunity, so they go for it, and we benefit
anyway.

I'd personally be happy with 10 second execution, but if I can get 1/2 second
execution, why would I complain?

------
amelius
> the story of high-frequency trading is basically one of small smart firms
> undercutting big banks by being smarter and more automated and more
> efficient

Is that true? Isn't there a high barrier of entry? I was under the impression
that large trading firms were building high-speed connections, which is
obviously not something a small firm could ever do.

~~~
juziozd
These days you can rent a co-located computer with direct connection to the
exchange. The cost is a few grands per month. Not very cheap but definitely
within reach of a small business. There are many small HF firms based all over
the country that just rent 1 or 2 computers close to exchanges. This is bad
for big investment banks like Goldman because they no longer have a location
advantage - you do not need an office in Manhattan to compete with big guys
anymore.

~~~
amelius
Then my followup question would be: why do we actually need trading to be
faster than the regular internet allows? For the objects being traded
(companies) have time-constants that are far greater than the millisecond-
range. And I hope the answer is not "because everybody else does it" :)

~~~
yummyfajitas
The answer is, in fact, "because everybody else does it".

[https://www.chrisstucchio.com/blog/2012/hft_apology2.html](https://www.chrisstucchio.com/blog/2012/hft_apology2.html)

This can be partially fixed with a very technocratic market microstructure
change (eliminating the subpenny rule). But politically that's very much a
"huh?" point - imagine Bernie Sanders saying "I believe we should let traders
quote in increments of 1/100 of a cent, not 1 cent".

[https://www.chrisstucchio.com/blog/2012/hft_whats_broken.htm...](https://www.chrisstucchio.com/blog/2012/hft_whats_broken.html)

(This would fix things on the placing orders side, but not on the cancelling
orders side.)

~~~
ctlby
Eliminating the sub-penny rule would probably be counter-productive for most
US equities. You would not see further spread compression (most stocks'
natural spreads are already greater than one cent), and displayed size would
likely shrink (this latter bit is exactly what happened when prices
decimalized). A better alternative would be a tick-size schedule that's a
function of price, as is generally done in Japan and Europe.

~~~
yummyfajitas
The "displayed size" would probably shrink, but so what? You'd just need to
look at the book to see it.

Decimalization would help even with equities where the natural size > 1c. HFTs
who want to get to the top of the book could compete by offering $10.0073
instead of racing to be the fastest at $10.0100. HFTs would compete on price
rather than speed.

~~~
ctlby
A more granular tick doesn't just "spread out" the existing liquidity to a
bunch of price levels--it meaningfully decreases incentives to post serious
size. The spread will end up being marginally tighter, but with thinner books,
you still pay more to trade large amounts. The objective function to minimize
is transaction costs, not spread.

~~~
beagle3
> it meaningfully decreases incentives to post serious size

Do you have support for that claim?

(I don't have an opinion; Trying to form one based on data)

~~~
ctlby
The second page contains a succinct summary of theoretical reasons why this is
true. The rest of the paper goes over empirical findings:
[http://www.acsu.buffalo.edu/~keechung/MGF743/Readings/G2%20D...](http://www.acsu.buffalo.edu/~keechung/MGF743/Readings/G2%20Decimalization.pdf)

Since then, we have additional data points from the decimalized US equity
markets. See
[http://www.sec.gov/rules/other/2014/34-72460.pdf](http://www.sec.gov/rules/other/2014/34-72460.pdf)
for a bibliography. The weight of the evidence points towards thinner books.
Incidentally, the SEC is looking to increase the tick size for illiquid small-
cap stocks for this very reason.

~~~
beagle3
Thanks!

------
devit
"Updating" orders seems a far more accurate terminology than "cancelling" in
the market maker case.

Although of course making such a distinction by law is problematic, because
updating an order to be "out-of-the-money" (have an absurdly low or high
price) is almost equivalent to canceling, and objectively determining if an
order is "out-of-the-money" is problematic.

------
astine
"Here you have an industry that has undercut the business of the big banks,
irritated hedge fund managers and been great for small investors. Why would
cracking down on that business be populist? Why would it alienate wealthy
donors?"

For the same reason that people don't generally cheer when a gang war happens.
Just because the gangsters are mainly shooting other gangsters doesn't mean
the violence isn't costly to society. The same with Wall Street. Just because
people don't trust big banks and suspect them of rooking the common man
doesn't mean that they want to legitimize said rooking, or that it isn't
costly to society when banks rip each other off.

~~~
kasey_junk
I think you are missing his point. HFT is not typically banks ripping each
other off. Its a new outside entity that has made the service the banks and
traditional market makers provided to their customers much cheaper at the
expense of hedge funds and bank profits.

In most industries we applaud this disruption.

~~~
astine
But, in the mind of the populist masses that Mr Levine it criticizing it is. I
don't work in finance and I'm not going to make any judgments on the industry,
just to say that people who are opposed to it would be opposed to HFTs as
well.

Also, the people who applaud 'disruption' are not this sort of populist, they
don't cheer because of the damage done to incumbents but because the
disruption will hopefully mean better products/services/prices for customers.
HFT just does the job of the old investment bankers slightly more efficiently.
If you think investment bankers are bad, you're not going to think that more
efficient investment are an improvement.

~~~
harryh
When ignorant people don't like something we should strive to explain the
benefits more clearly. Not give up and declare that thing bad just based on a
vote.

------
blazespin
Ahem, buried in the middle of the article (I wonder why) "Navinder Sarao is
accused of spoofing in the S&P 500 futures market, entering and cancelling
lots of orders to create an illusion of demand, in suspicious proximity to the
flash crash of 2010."

This happens a lot more than you might think. There is always a temptation to
stuff the order book to keep it going in a direction profitable for you (ie,
fake volatility).

This is the #1 reason why canceled ordered from HFT are suspect. It's too easy
to stuff the order book and cheat a little. You really need highly credible
market makers who have proven not to do this sort of thing. Even then, such
folks are very rare and hard to appreciate. Your algorithms get so complex and
obfuscated it's hard to tell what's stuffing the order book and what's simple
market making.

The fact is, everyone is stuffing the order book. Sarao is more a patsy than
anything else. His biggest crime wasn't belonging to a Goldman Sachs paying
bribes to political entities.

~~~
tptacek
_There is always a temptation to stuff the order book to keep it going in a
direction profitable for you (ie, fake volatility)._

Is this something you have personal experience in? I ask because a lot of
people relate this concern because they read about it in Zero Hedge, which is
regarded by people in the industry as (as someone here once put it) "a
conspiracy theory site without the theories".

~~~
beagle3
The description of ZeroHedge is funny and not entirely untrue, but if you
regard them as an aggregator of opinions, (which they mostly are, even though
they do offer their own opinions), it is unmatched in its breadth of coverage,
despite having a rather low signal coverage.

WRT suffing the order book - at least as far back as 2003, in Eurex, there was
a swiss trader who would do that in bond futures. There were a lot of
comlpaints, and even death threats IIRC, but a Eurex investigation at the time
found he did nothing wrong - their main finding was that he would occasionally
get those "stuffing" orders executed, which means that (as far as they are
concerned) they are not false or misleading in any way.

That's probably the gist of it: as long as you are willing to take the hit if
your bluff goes against you, there's nothing "fake" about it. It's been years
since, and I know not of any (officially investigated) cases back then, or of
any recent cases - but I'd be surprised if it's not very prevalent. (Also,
I've been out of the HFT world for a while).

------
mjevans
A better question is why do we even have 'High Frequency Traders'?

Wouldn't the market be better served by a window structure with a scale on a
more human timespan? Say a 5 min process in which:

* for 4 min orders are taken in confidential secret.

* there is a 1 min blackout window in which no orders are taken, and in which any results of settling the outcome of orders is not published.

* At the end of that period the new results are published. (It doesn't matter who reacts first, it's who reacts best.)

The profit between what sellers are asking for and what the buyers are willing
to pay still needs to be accounted for. This could be the market's operating
fee (the cost of the sale's commission), it could be attributed to the
government as a form of sales tax, it could be returned in some way to the
parties involved (buyers pay less, sellers earn more), other, or some
combination of the above.

~~~
jrockway
The price of equities is not known. The market is how that price is
calculated.

You could slow down the process, but that adds risk (that one party is getting
the wrong price). The market makers would say, I'll sell you one 1 share for
$1, 10 shares for $1.20, 100 shares for $2, 1000 shares for $10. So then
someone who wants to buy 1000 shares for $1 a share will buy only 1 share at
$1. Then in the quiet period, the market makers will adjust their prices. 1
share for $1.01, etc. Then you'll sell another share for $1.01. Then you'll
wait 5 minutes, and the market makers will adjust their price.

The market is going to work the same way at 5 minute delay as it works at
nanosecond delay, but just be slower. The market makers won't be getting you a
better price, and your large transaction won't not affect the share price.

------
shasta
I guess I see why high frequency trades are necessary in the current trading
framework, but looking at the situation from a high level, isn't it obvious
that the resources being spent on microsecond level response improvements
don't benefit anyone but the winners? Can someone argue otherwise?

~~~
tptacek
You're right, although you should also build into that argument the benefits
that accrue to technologists that work at HFT firms, and to technology vendors
who sell to them.

~~~
idlewords
And to HFT simulation writers!

~~~
tptacek
Well, fuck.

------
frandroid
TL;DR: Market makers put a buy and a sell offer, separated by one or more
cents, on every trade; when someone big enough picks one side, they cancel the
other side and re-issue new buy and sell offers with new goal-posts.

------
ehosca
it's called "discovery" ...

------
Variance
It's great to see Matt Levine on HN - for those interested in finance, his
Money Stuff [0] daily column is absolutely excellent. His writing has a really
fantastic funny and informal style.

He does a great job presenting a fair and deep view of a lot of finance
issues, like HFT or Unicorn valuations.

[0] [http://www.bloombergview.com/topics/money-
stuff](http://www.bloombergview.com/topics/money-stuff)

~~~
jevgeni
Matt is brilliant. A little bit more mature and reserved than during his time
at Dealbreaker, but still awesome.

------
curiousjorge
what benefit does high frequency traders provide to rest of society? none.
they raise the cost of transactions of all investors. it should be banned and
those brought to justice.

------
MisterMashable
Legalized quote stuffing.

------
NickHaflinger
Because they're gaming the market. How it works: place a large order, wait for
others to make a bid, then cancel the order and sell your own at a mark-up.

