[sichtlinkair]

> It's likely to be a "picking up pennies in front of a steamroller" type trade.

What does that mean?

[bryanlarsen]

If there's a highway made of pennies that is being maintained by a steamroller, you can make a very consistent but small profit by picking up pennies every day. Except for that one day that you get run over by a steamroller.

A better example is imagine that every day you bet on coin flips. Every day you go home after you're up $1. You start off with a $1 bet, and double the bet every time you lose. So for example one day, you might lose $1, then lose $2, then win $4 for a total profit of $1.

It's a foolproof strategy! You win $1 every day and you can't lose. But of course it assumes that both you and the house have an infinite stake. But if not, one day the house flips 16 heads in a row and you don't have $65536 to bet a 17th time so you go home down $65535. Kind of makes your $1 daily wins look pretty stupid now, doesn't it?

There are tons of options plays available on the stock market that have a risk profile similar to the coin flip example.

[slv77]

This is called a martingale bet (https://en.m.wikipedia.org/wiki/Martingale_(betting_system)). Doubling down on losses would be an example of a martingale bet.

[jiscariot]

I think this is also a reason why tables generally have set limits.

[confidantlake]

I don't think so. If you as the player make bets a series of bets, each with a negative expected value then your total expected value will also be negative. It doesn't matter if you double after every loss.

The limits are mostly because the casino can't afford to take on a 20 billion dollar bet from someone like Bezos. Even if it has a positive expected value, they will still go broke the 49% of the time they lose it.

[j7ake]

The martingale strategy works because this theoretical gambler has infinitely deep pockets to withstand the losses.

Setting bet limits can reduce the effectiveness of the martingale strategy.

[confidantlake]

I don't think it matters, even with infinite pockets. Let's say 3 is the max number of losses we will accept. 50-50 coin flip, start of betting a dollar. 7 out of 8 times we win a dollar. 1 out of 8 time we lose a dollar, double lose 2 dollars, double, lose 4 dollars quit.

(7/8)(1) + (1/8)(-7) = 0

Generally: n = number of losses before quit.

E(x) = (1-.5^n)(1) + (.5^n)(-2^n+1)

     = (1) - (1/2^n) - (2^n-1)/(2^n)
     

     = (2^n)/(2^n) - 1/(2^n) - (2^n+1) / (2^n)
     
     = (2^n -1 - 2^n + 1) / (2^n)
     
     = 0

So with a 50-50 our expected value is 0 even with an infinite bankroll. Which makes sense, there is no way to transform a series of neutral or negative expected value bets into a positive expected bet by combining them.

[ahelwer]

Think of a slowly advancing steamroller, with pennies scattered before it. You can run around picking up these pennies, for small but consistent gain over a long period of time. Just don't take your eye off the steamroller!

The canonical example in recent times is the XIV blowup of 2018, which inversed VIX (a security tracking market volatility). So if you held XIV you basically bet that large market moves wouldn't happen - you're shorting volatility. Take a look at the graph to see how that ended up; the steamroller caught up to them! https://www.rcmalternatives.com/2018/02/why-did-xiv-implode/

[kesselvon]

There are trades where you can make a small profit regularly, but on bad days you take huge losses. The huge losses outweigh all the potential profits by a large margin. Just like picking up pennies is a small gain while risking death to do so

[ahelwer]

Traders who engage in such behavior are also humorously said to "eat like chickens, shit like elephants"

[b0afc375b5]

I think it means doing something high risk for low reward.

[kccqzy]

It means doing something high risk but the risk has low probability, and for low reward.

No rational mind would do anything high risk low reward, unless the risk has low probability. Then it's just like selling insurance.

[skrtskrt]

A good example is selling options for premium.

You can sell a put option against a stock.

Say the stock is $100 right now, and you sell a put option one month out for a strike price of $90.

The seller of this put option essentially bets that the stock will still be above $90 in a month.

The buyer of this put option is betting that the stock will be below $90 in a month.

For executing this trade, you, the put seller, receive premium, say $1. The buyer pays you $1.

You have a sold a very high likelihood bet and received $1 for taking on the risk. The buyer has bought a very low likelihood bet and spent $1 for the chance to win.

This sounds great! In the long run, stocks tend to go up so you should win this bet the vast majority of the time, collect your $1, and make the same bet again.

This is the "picking up pennies" stage.

Now what is the steamroller? The steamroller is the low likelihood but very high loss scenario that this stock or ETF absolutely crashes while you are on the selling side of this open put option bet.

If it crashes to $N where $N < $90, the put option buyer has the option or right to sell you the stock at $90, even if it is worth hardly anything. So you have now paid $90 for a stock worth less than $90. It could be $0, the company could be bankrupt. Your loss is -($90-N)+$1. (Note that because of your $1 premium, your breakeven on this trade is when the stock is at $89, not $90.)

If you put up the collateral (the money needed to buy the stock at $90) for the bet with your own money, you are out that money. If you put up collateral on margin (borrowed money) you can be mega screwed.

This is the steamroller. You picked up $1 here and and there but then you got hit with a -$20 or -$50 or -$90 steamroller when you may have not even had the money to cover it.

Yes the steamroller is very low likelihood, but you have to hit pick up a LOT of pennies in a row to still come out on top after getting hit by the steamroller.

It is important to note that there is a ton more nuance that can go into running this kind of strategy, but in general for the average person, buy and hold will always outperform a strategy like this for several reasons, not least of them being that the income received for premium is taxed at income rates, where gains from buy and hold will be taxed at capital gains rates.

Very sophisticated investors do run this strategy with many ways to handle the tail risk, and their sophisticated strategies do not necessarily stop them from getting absolutely screwed when things go bad like during the flash crash at the beginning of coronavirus. Modeling and mitigating tail risk is hard, because terrible events are not as common as normal events and when things go terribly, they usually go terribly in a way no one has ever seen before.

[jdasdf]

Just a quick note here, selling puts is actually the worse of the examples you could have mentioned, because you can simply use it as a way to maintain an open order for the stock at a given price while getting paid for it.

Selling calls would be a better example, since in that case losses are potentially limitless.

[skrtskrt]

True, but a casual investor is less likely to sell naked calls with infinite loss.

When they sell covered calls and lose the bet, the only loss is missing out on the run up of the stock.

I mostly just used the put example because it maps better to compare to a buy and hold strategy - good if market is up, bad if market is down.

It's also a well-known pennies-in-front-of-steamroller strategy that hedge funds have gotten very publicly burned on before, so anyone interested could research more.

[kccqzy]

Your trades have a near-zero (probably positive) mean but very negative skewness.

[MR4D]

It means doing something very risky for little overall gain.

[paulpauper]

it's like shoplifitng. big penalty if caught, small reward if you get away with it, which most do until too late. asymetical payoff.