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Technical analysis doesn't work. Big surprise you lost money. Those guys that you thought were good at it? They lost their shorts at some point too.



My first job out of college was building a TA package at a then-small Bloomberg competitor. I knew basically nothing about any of this and just approached it as a technical challenge, and I had a generally ok time just getting paid to write software that was vaguely mathy. This was software that was actually used by people trading, who were paying on the order of tens of thousands of dollars a year per seat.

The first signs that something was amiss arose pretty early. I kept some printouts of what the various metrics were in my desk. Occasionally a support employee would come over and say so-and-so at some bank wants to know how (say) Bollinger Bands are defined. I'd hand them a copy of my definitions sheet covered in capital pi's and sigmas. They'd look at it, their eyes would glaze over, they'd wander away, and I never got a single followup question.

About four years later a client discovered that there'd been a bug in a few of the calculations that made them wildly "incorrect." Many people used the product for years as happy customers without realizing this.

At that point I must have googled "technical analysis wtf" or something, and realized that basically what I had been spending my time on was the financial equivalent of biblical numerology. So it goes.


I'm wrong all the time and lose money all the time. The big difference here is I let one get away from me instead of keeping it small/manageable like I always do. It was a situation where I could have controlled it and I didn't. I'm still up more than 4x what the final realized loss was in my trading career.

I used to think TA was a joke. I was very skeptical before using it. I have never bothered to explain why it works intellectual to non-believers. But I do think someone who understood probability and saw the compiled statistics of practitioners would concede that there's 0 chance of non-randomness.


Yeah, no. That's called anecdotes, because when you do understand probability and backtest these strategies, they are known not to work in the large.

Stat arb is what happens when you actually do statistics, and these days it's got only a slim to nil advantage.


Trading is like the Israeli nuclear program: those who talk about it don't know about it, those who know about it don't talk about it.

If technical analysis actually worked, you'd be able to find the "Technical Analysis Toolkit" for on GitHub, and... technical analysis would no longer work. A little bit of grepping around yields: http://ta-lib.org/ (Technical Analysis Lib).

Ergo: if technical analysis ever worked (there is some evidence it did before about 1990 when personal computers became ubiquitous) it almost certainly does not today.

The only way market timing approaches can work is if they embody significant information that is not generally available. A successful market timer has to be smarter than everyone else in the market at the time of each trade.

Anyone claiming technical analysis works is claiming that there is an inefficiency in the market that has been well-documented in public for decades, to the extent that an open-source BSD-licensed tool for identifying the inefficiency exists, and yet the inefficiency still exists.

This is simply contradictory.


An economics professor is walking down the street with a student. The student sees a $100 bill on the ground and tells the professor. The professor says, "Nonsense! If there were a bill on the ground, someone would have picked it up already!"

I actually think that in this case you are probably right, though. But I wouldn't bet my life on it.


I love this joke, because on the surface it's making fun of economists whose theories blind them to an obvious reality. But how often does anyone actually find a $100 bill on the ground?


I found a 20 on the ground by a gas station pump. Its not improbable that someone taking their keys or wallet out would accidentally drop any loose bills they had.


My wife found one once on a very windy day in Denver.



Of course not every idea ever has been tried. But there's a lot of incentive.

Statistically it would be ok to bet your life on it, though.

Did you hear the one about the economist who drowned crossing a river that was three feet deep on average?


Haven't heard that one until now that you mention it, nice.


You sound like the people I've seen on gambling forums postings about their unbeatable roulette system that they've "really won with in the long term".


There are actually ways to beat roulette.

1. Observe the motion of the ball and the wheel between the time they start moving and the time betting is closed, and use physics to calculate where the ball is likely to land. Bet accordingly. This was proven effective in the early '80s [1].

2. Record a lot of outcomes on a given wheel to learn its biases. Bet accordingly. You might think it would be hard to surreptitiously gather all the data you would need, but it is made considerably easier because you do not have to be surreptitious. Casinos love people who are taking notes--99.999% of the time it means that is someone who has some idiotic system that they think will let them beat the house, and casinos want to encourage such people.

There was an episode of the wonderful documentary series "Breaking Vegas" [2] that covered this method, focusing on a family that practiced it. They were making a lot of money until the Las Vegas and Atlantic City casinos banned them. American casinos can ban you for winning too much, even if you are not in any way cheating. They switched to Europe, where the casino regulators prohibited the casinos from banning them without cause, and "winning to much without cheating" is not cause. The casinos tried moving the wheels to different tables to confuse the family, but the family had spent so much time looking at each wheel they could recognize individual wheels be wear patterns and place the appropriate bets. It was pretty cool.

3. My favorite, even though it was flat out cheating. This was also covered on a "Breaking Vegas" episode. Before I explain this cheating method, we need to take a look at an older cheating method that is no longer effective. That was "past posting" or "late betting". In past posting, you place a bet AFTER the outcome of the event you are betting on has been determined. So in roulette that would be placing a bet after the ball has fallen into its final slot.

Of course, that would be hard to do. The risk would be too high that the operator might have noticed that there were no bets on that particular number when betting closed. So what you actually did was modify a winning bet after the fact to make it bigger. You put, say, a stack of 3 of the lowest value chips on a number. If that number loses, you lose those chips. If it wins, the rest of your team distracts the operator, and you swap that stack of 3 low value chips for a stack that consists of 2 low value chips on top and 1 high value chip on the bottom.

There was a guy who was doing a lot of past posting on the roulette tables, back before they had constant recorded closed circuit TV surveillance. The casinos suspected he was doing something to cheat, because he was winning more than they would like (but not enough to get banned), but they couldn't catch what he was doing.

Then surveillance came, and when he would win with a stack of 2 low value and 1 high value chip instead of paying right away they would detain him while they pulled the tape and reviewed it to see if they could see any shenanigans. He had to stop past posting. His career as a roulette cheat seemed over.

And then he had a brilliant idea. Instead of cheating by converting low value winning bets into high value winning bets, why not go the other way? Convert high value losing bets into low value losing bets!

The new plan was to place bets consisting of a high value chip on bottom with some low value chips on top, with the low value chips positioned so that the operator would not see the high value chip. It would look to him like a stack of low value chips.

If their bet lost, they would swap the stack for a stack of all low value chips. If their bet won, they would not touch it, and point out to the operator that there was a high value chip there so they would get the right pay off.

The casinos were, of course, very suspicious. They recognized that they were dealing with a known past poster, so every time he won they pulled the tape...and the tape showed that no one had come near fiddling with the winning bet. The high value chip had been at the bottom of the stack from the moment the bet was placed.

He got away with this for a ridiculous amount of time, with the head of security from one of the major casinos reviewing every win and getting quite frustrated at not being able to catch how the cheat was working. I forget how he finally got caught.

BTW, I highly recommend "Breaking Vegas". They profile some remarkable people, some who cheat, and some who won legitimately. A couple neat examples.

• They have an episode on dice dominators. These are people who, through great practice, can roll the dice at craps with such control and consistency as to get the outcome they want much more often than by chance.

• They have an episode on a man who took up counterfeiting slot machine tokens. The casinos detected this because they were getting high token counts at the end of the day, but they could not tell which tokens were counterfeit. They sent batches back to the manufacturer, and the manufacturer said that all the tokens that were sent were real.

His downfall was interesting. He was playing a slot machine that took something like $25 tokens, and the machine jammed. He moved over to the next machine and continued playing. Security happened to see that on camera, and that made them suspicious. The normal behavior when someone loses a $25 token to a jammed machine is for that person to get mad, and go find casino staff to seek a refund. No one just moves over to the next machine and keeps going--unless that $25 token isn't worth $25 to them. Hence, the guard thought he might be looking at the infamous token counterfeiter. They followed him to the parking lot when he left, and when he opened the trunk of his car that he had boxes full of tokens for all the major casinos.

[1] http://en.wikipedia.org/wiki/The_Eudaemonic_Pie

[2] http://en.wikipedia.org/wiki/Breaking_Vegas


Wow! Fascinating comment. I'm going to have to check out "Breaking Vegas".


Yeah, I alo made a fortune in the market except for the money I lost.


I recall seeing a graph of a stock index in which all but the 10 (e.g.) best days within a very long time span (~years) were removed - to mock up a trader who removed his money at a few unlucky times. You ended up losing huge.

The lesson was exactly what you're saying -- you also have to count that one huge loss. You can't fence it off as an exception and remove it from the accounting.


Wealthfront posted a graph on that. I called them out on it on Twitter which they didn't appreciate.


Url please?


https://blog.wealthfront.com/much-liquidity-will-cost-long-r...

Not sure how to find the Twitter interaction as Twitter isn't big on history as far as I understand it.


Thanks for finding the plot.


Yep, I tried to find the graph but failed. It would be interesting to see again. I have a professional interest in probability and stochastic processes, so it stuck in my mind.


I have seen the graph before, I was curious about the response on Twitter.





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