If the Efficient Market Hypothesis is true, shouldn’t it be almost as hard to lose money on the market as it is to gain money? Let’s say you had a strategy S that reliably loses money. Shouldn’t you be able to define an inverse strategy S’, that buys when S sells and sells when S buys, that reliably earns money? For the sake of argument rule out obvious errors like offering to buy a stock for $1 more than its current price.
I guess the difference is that if you offer to sell a ton of gold for $1, you will find a buyer, but if you offer to buy a ton of gold for $1, you will not find a seller.
The inverse strategy will not produce the inverse result.
shouldn’t it be almost as hard to lose money on the market as it is to gain money?
Consider the dynamic version of the EMH: that is, rather than “prices are where they should be,” it’s “agents who perceive mispricings will pounce on them, making them transient.”
Then a person placing a dumb trade is creating a mispricing, which will be consumed by some market agent. There’s an asymmetry between “there is no free money left to be picked up” and “if you drop your money, it will not be picked up” that makes the first true (in the static case) and the second false.
Then a person placing a dumb trade is creating a mispricing, which will be consumed by some market agent.
Well, that looks like an “offering to buy a stock for $1 more than its current price” scenario. You can easily lose a lot of money by buying things at the offer and selling them at the bid :-)
But let’s imagine a scenario where everything is happening pre-tax, there are no transaction costs, we’re operating in risk-adjusted terms and, to make things simple, the risk-free rate is zero. Moreover, the markets are orderly and liquid.
Assuming you can competently express a market view, can you systematically lose money by consistently taking the wrong side under EMH?
Consider penny stocks. They are a poor investment in terms of expected return (unless you have secret alpha). But they provide a small chance of very high returns, meaning they operate like lottery tickets. This isn’t a mispricing—some people like lottery tickets, and so bid up the price until they become a poor investment in terms of expected return (problem for the CAPM, not for the EMH). So you can systematically lose money by taking the “wrong” side, and buying penny stocks.
Does that count as an example, or does that violate your “risk-adjusted terms” assumption? I think we have to be careful about what frictions we throw out. If we are too aggressive in throwing out notions like an “equity premium,” or hedging, or options, or market segmentation, or irreducible risk, or different tolerances to risk, we will throw out the stuff that causes financial markets to exist. An infinite frictionless plane is a useful thought experiment, but you can’t then complain that a car can’t drive on such a plane.
Let’s take penny stocks. First, there is no exception for them in the EMH so if it holds, the penny stocks, like any other security, must not provide a “free” opportunity to make money.
Second, when you say they are “a poor investment in terms of expected return”, do you actually mean expected return? Because it’s a single number which has nothing do with risk. A lottery can perfectly well have a positive expected return even if your chance of getting a positive return is very small. The distribution of penny stock returns can be very skewed and heavy-tailed, but EMH does not demand anything of the returns distributions.
So I think you have to pick one of two: either penny stocks provide negative expected return (remember, in our setup the risk-free rate is zero), but then EMH breaks; or the penny stocks provide non-negative expected return (though with an unusual risk profile) in which case EMH holds but you can’t consistently lose money.
Does that violate your “risk-adjusted terms” assumption?
My “risk-adjusted terms” were a bit of a handwave over a large patch of quicksand :-/ I mostly meant things like leverage, but you are right in that there is sufficient leeway to stretch it in many directions. Let me try to firm it up: let’s say the portfolio which you will use to consistently lose money must have fixed volatility, say, equivalent to the volatility of the underlying market.
Second, when you say they are “a poor investment in terms of expected return”, do you actually mean expected return? … A lottery can perfectly well have a positive expected return even if your chance of getting a positive return is very small.
Yes, I mean expected return. If you hold penny stocks, you can expect to lose money, because the occasional big wins will not make up for the small losses. You are right that we can imagine lotteries with positive expected return, but in the real world lotteries have negative expected return, because the risk-loving are happy to pay for the chance of big winnings.
[If] penny stocks provide negative expected return … then EMH breaks
Why?
Suppose we have two classes of investors, call them gamblers and normals. Gamblers like risk, and are prepared to pay to take it. In particular, they like asymmetric upside risk (“lottery tickets”). Normals dislike risk, and are prepared to pay to avoid it (insurance, hedging, etc). In particular, they dislike asymmetric downside risk (“catastrophes”).
There is an equity instrument, X, which has the following payoff structure:
99% chance: payoff of 0
1% chance: payoff of 1000
Clearly, E(X) is 10. However, gamblers like this form of bet, and are prepared to pay for it. Consequently, they are willing to bid up the price of X to (say) 11.
Y is the instrument formed by shorting X. When X is priced at 11, this has the following payoff structure:
99% chance: payoff of 11
1% chance: payoff of −989
Clearly, E(Y) is 1. In other words, you can make money, in expectation, by shorting X. However, there is a lot of downside risk here, and normals do not want to take it on. They would require E(Y) to be 2 (say) in order to take on a bet of that structure.
So, assuming you have a “normal” attitude to risk, you can lose money here (by buying X), but you can’t win it in risk-adjusted terms. This is caused by the market segmentation caused by the different risk profiles. Nothing here is contrary to the EMH, although it is contrary to the CAPM.
Thoughts:
Penny stocks (and high-beta instruments generally, such as deep out-of-the-money options) display this behaviour in real life.
A more realistic model might include some deep-pocketed funds with a neutral attitude to risk who could afford to short X. But in real life, there is market segmentation and a lack of liquidity. Penny stocks are illiquid and hard to short, and so are many other high-beta instruments.
The logical corollary of this model is that safe, boring equities will outperform stocks with lottery-ticket-like qualities. And it therefore follows that safe, boring equities will outperform the market as a whole. And that also seems true in real life.
There are plausible microfoundations for why there might be a “gambler” class of investor. For example, fund managers are risking their clients’ capital, not their own, and are typically paid in a ranking relative to their peers. Their incentives may well lead them to buy lottery tickets.
However, there is a lot of downside risk here, and normals do not want to take it on.
By itself, no. But this is diversifiable risk and so if you short enough penny stocks, the risk becomes acceptable. To use a historical example, realizing this (in the context of junk bonds) is what made Michael Milken rich. For a while, at least.
market segmentation caused by the different risk profiles
This certainly exists, though it’s more complicated than just unwillingness to touch skewed and heavy-tailed securities.
Penny stocks (and high-beta instruments generally, such as deep out-of-the-money options) display this behaviour in real life.
In real life shorting penny stocks will run into some transaction-costs and availability-to-borrow difficulties, but options are contracts and you can write whatever options you want. So are you saying that selling deep OOM options is a free lunch?
As for the rest, you are effectively arguing that EMH is wrong :-)
Who says this risk is diversifiable? Nothing in the toy model I gave you said the risk was diversifiable. Maybe all the X-like instruments are correlated.
No, I’m not saying that selling deep OOM options is a free lunch, because of the risk profile. And these are definitely not diversifiable.
I am not arguing that EMH is wrong. I have given you a toy model, where a suitably defined investor cannot make money but can lose money. The model is entirely consistent with the EMH, because all prices reflect and incorporate all relevant information.
Oh, I thought we were talking about reality. EMH claims to describe reality, doesn’t it?
As to toy models, if I get to define what classes of investors exist and what do they do, I can demonstrate pretty much anything. Of course it’s possible to set up a world where “a suitably defined investor cannot make money but can lose money”.
And deep OOM options are diversifiable—there is a great deal of different markets in the world.
Oh, I thought we were talking about reality. EMH claims to describe reality, doesn’t it?
Yeah, but you wanted “a scenario where everything is happening pre-tax, there are no transaction costs, we’re operating in risk-adjusted terms and, to make things simple, the risk-free rate is zero. Moreover, the markets are orderly and liquid.” That doesn’t describe reality, so describing events in your scenario necessitates a toy model.
In the real world, it is trivial to show how you can lose money even if the EMH is true: you have to pay tax, transaction costs are non-zero, the ex post risk is not known, etc.
deep OOM options are diversifiable—there is a great deal of different markets in the world.
There’s still a lot of correlation. Selling deep OOM options and then running into unexpected correlation is exactly how LTCM went bust. It’s called “picking up pennies in front of a steamroller” for a reason.
That doesn’t describe reality, so describing events in your scenario necessitates a toy model.
Fair point :-) But still, with enough degrees of freedom in the toy model, the task becomes easy and so uninteresting.
It’s called “picking up pennies in front of a steamroller” for a reason.
I know. Which means you need proper risk management and capitalization. LTCM died because it was overleveraged and could not meet the margin calls. And LTCM relied on hedges, not on diversification.
Since deep OOM options are traded, there are people who write them. Since they are still writing them, it looks like not a bad business :-)
Yes. Unless you think that all possible market information is reflected now, before it becomes available, someone makes money when information emerges, moving the market.
Yes, you can (theoretically) make money by front-running the market. But I don’t think you can systematically lose money that way (and stay within EMH) and that’s the question under discussion.
We’re talking about ways to systematically lose money, which means you would need to systematically throw yourself into the front-runner’s path, which means you would know where that path is, which means you can systematically forecast the front-running. I think the EMH would be a bit upset by that :-)
We’re talking about ways to systematically lose money, which means you would need to systematically throw yourself into the front-runner’s path
Simply making random trades in a market where some participants are front runners will mean that some of those trades are with front runners where you lose money.
I would call that systematically losing money. On the other hand it doesn’t give you an ability to forcast where you will lose the money to make the opposite bet and win money.
Do you think our disagreement is about the way the EMH is defined or are you pointing to something more substantial?
I think you’re mistaken about that. As an empirical fact, it depends. What you are missing is the mechanism where when you sell a stock short, you don’t get to withdraw the cash (for obvious reasons). The broker keeps it until you cover your short and basically pays you interest on the cash deposit. Right now in most of the first world it’s miniscule because money is very cheap, that that is not the case always or everywhere.
It is perfectly possible to short a stock, cover it at exactly the same price and end up with more money in your account.
Actually, when you short a stock, you must pay an interest rate to the person from whom you borrowed the stock. That interest rate varies from stock to stock, but is always above the risk-free rate. Thus, if you short a stock and do nothing interesting with the cash and eventually cover it at the original price, you will lose money.
If you enter into a short sale at time 0 and cover at time T, you get paid interest on your collateral or margin requirement by the lender of the asset. This is called the short rebate or (in the bond market) the repo rate. As the short seller, you’ll be required to pay the time T asset price along with lease rate, which is based on the dividends or bond coupons the asset pays out from 0 to T.
So, if no dividends/coupons are paid out, it’s theoretically possible for you to profit from selling short despite no change in the underlying asset price.
The lease rate is an interest rate (ie, based on time) in addition to the absolute minimum payment of the dividends issued. It is set by the market: there is a limited supply of shares available to be borrowed for shorting. For most stocks it is about 0.3% for institutional investors, but 5% for a tenth of stocks. The point is that this is an asymmetry with buying a stock.
Now that I look it up and see that it is 0.3%, I admit that is not so big, but I think it is larger than the repo rate. I see no reason for the lease rate to be related to inflation, so in a high inflation environment, you could make money by shorting a stock that did not change nominal price.
(Dividends are not a big deal in shorting because the price of a stock usually drops by the amount of the dividend, for obvious reasons.)
I think you’re mistaken about that. As an empirical fact, it depends. What you are missing is the mechanism where when you sell a stock short, you don’t get to withdraw the cash (for obvious reasons). The broker keeps it until you cover your short and basically pays you interest on the cash deposit. Right now in most of the first world it’s miniscule because money is very cheap, that that is not the case always or everywhere.
Maybe if you have the right connections, and the broker really trust you. The issue is suppose you short a stock, the price goes up and you can’t cover it. Someone has to assume that risk, and of course will want a risk premium for doing so.
Maybe if you have the right connections, and the broker really trust you.
It doesn’t have anything to do with connections or broker trust. It’s standard operating practice for all broker clients.
The issue is suppose you short a stock, the price goes up and you can’t cover it.
If the price goes sufficiently up, you get a margin call. If you can’t meet it, the broker buys the stock to cover using the money in your account without waiting for your consent. The broker has some risk if the stock gaps (that is, the price moves discontinuously, it jumps directly from, say, $20 to $40), but that’s part of the risk the broker normally takes.
Another thing to watch out for when shorting stocks is dividends. If you are short a stock on the ex dividend date, then you have to pay the dividend on each share that you have shorted. However, as long as you keep margin calls and dividends in mind, short selling is a good technique (and an easy one) to play a stock that you are bearish on.
And, no, you don’t need any special connections, although you typically need to request short-selling privileges on your brokerage account.
Another way to play a stock you are bearish on is buying put options. But put options are a lot harder to use effectively because (among other reasons) they become worthless on the expiration date.
Yes, for strategies with low enough transaction costs (i.e. for most buy-and-hold like strategies, but not day-trading).
It will be somewhat hard for ordinary investors to implement the inverse strategies, since brokers that cater to them restrict which stocks they can sell short (professional investors usually don’t face this problem).
The EMH is only a loose approximation to reality, so it’s not hard to find strategies that underperform on average by something like 5% per year.
The EMH works because everybody is trying to gain money, so everybody except you trying to gain money and you trying to lose money isn’t the symmetric situation. The symmetric situation is everybody trying to lose money, in which case it’d be pretty hard indeed to do so. And if everybody except you was trying to lose money and you were trying to gain money it’d be pretty easy for you to do so. I think this would also be the case in absence of taxes and transaction costs. IOW I think Viliam nailed it and other people got red herrings.
Hugely important to distinguish between investing and trading here. But the short answer is that it’d be near impossible to lose money systematically without knowing the inverse (more profitable) strategy.
Consider the scenario where a 22-year-old teacher named Warren, who knows nothing about finance, takes 80% of his annual salary and buys random stocks with the intent to hold until retirement age (reinvesting all dividends). It would be extraordinarily fluky for him to not make solid returns over the long-run with this approach, let alone break even or lose money, as all publicly traded stocks have reasonably high positive expected value.
Now consider derivatives trading. Even if we assume no transaction costs, it’d be near-impossible for Warren to not lose money over the long-run by partaking in lots of random bets with, at best, 0 expected value. Your term, “the market” is problematic because “the market” can act as a bank or a poker table depending on the purchases of the investor.
EMH implies that it’s not easy to make a living through financial trading. It’s incredibly easy to slowly leak money to those who are making a living at it, though. Unlike buying stocks, bonds, etc., financial trading is zero-sum.
If the Efficient Market Hypothesis is true, shouldn’t it be almost as hard to lose money on the market as it is to gain money? Let’s say you had a strategy S that reliably loses money. Shouldn’t you be able to define an inverse strategy S’, that buys when S sells and sells when S buys, that reliably earns money? For the sake of argument rule out obvious errors like offering to buy a stock for $1 more than its current price.
I guess the difference is that if you offer to sell a ton of gold for $1, you will find a buyer, but if you offer to buy a ton of gold for $1, you will not find a seller.
The inverse strategy will not produce the inverse result.
Consider the dynamic version of the EMH: that is, rather than “prices are where they should be,” it’s “agents who perceive mispricings will pounce on them, making them transient.”
Then a person placing a dumb trade is creating a mispricing, which will be consumed by some market agent. There’s an asymmetry between “there is no free money left to be picked up” and “if you drop your money, it will not be picked up” that makes the first true (in the static case) and the second false.
Well, that looks like an “offering to buy a stock for $1 more than its current price” scenario. You can easily lose a lot of money by buying things at the offer and selling them at the bid :-)
But let’s imagine a scenario where everything is happening pre-tax, there are no transaction costs, we’re operating in risk-adjusted terms and, to make things simple, the risk-free rate is zero. Moreover, the markets are orderly and liquid.
Assuming you can competently express a market view, can you systematically lose money by consistently taking the wrong side under EMH?
Consider penny stocks. They are a poor investment in terms of expected return (unless you have secret alpha). But they provide a small chance of very high returns, meaning they operate like lottery tickets. This isn’t a mispricing—some people like lottery tickets, and so bid up the price until they become a poor investment in terms of expected return (problem for the CAPM, not for the EMH). So you can systematically lose money by taking the “wrong” side, and buying penny stocks.
Does that count as an example, or does that violate your “risk-adjusted terms” assumption? I think we have to be careful about what frictions we throw out. If we are too aggressive in throwing out notions like an “equity premium,” or hedging, or options, or market segmentation, or irreducible risk, or different tolerances to risk, we will throw out the stuff that causes financial markets to exist. An infinite frictionless plane is a useful thought experiment, but you can’t then complain that a car can’t drive on such a plane.
Yes, we have to be quite careful here.
Let’s take penny stocks. First, there is no exception for them in the EMH so if it holds, the penny stocks, like any other security, must not provide a “free” opportunity to make money.
Second, when you say they are “a poor investment in terms of expected return”, do you actually mean expected return? Because it’s a single number which has nothing do with risk. A lottery can perfectly well have a positive expected return even if your chance of getting a positive return is very small. The distribution of penny stock returns can be very skewed and heavy-tailed, but EMH does not demand anything of the returns distributions.
So I think you have to pick one of two: either penny stocks provide negative expected return (remember, in our setup the risk-free rate is zero), but then EMH breaks; or the penny stocks provide non-negative expected return (though with an unusual risk profile) in which case EMH holds but you can’t consistently lose money.
My “risk-adjusted terms” were a bit of a handwave over a large patch of quicksand :-/ I mostly meant things like leverage, but you are right in that there is sufficient leeway to stretch it in many directions. Let me try to firm it up: let’s say the portfolio which you will use to consistently lose money must have fixed volatility, say, equivalent to the volatility of the underlying market.
Yes, I mean expected return. If you hold penny stocks, you can expect to lose money, because the occasional big wins will not make up for the small losses. You are right that we can imagine lotteries with positive expected return, but in the real world lotteries have negative expected return, because the risk-loving are happy to pay for the chance of big winnings.
Why?
Suppose we have two classes of investors, call them gamblers and normals. Gamblers like risk, and are prepared to pay to take it. In particular, they like asymmetric upside risk (“lottery tickets”). Normals dislike risk, and are prepared to pay to avoid it (insurance, hedging, etc). In particular, they dislike asymmetric downside risk (“catastrophes”).
There is an equity instrument, X, which has the following payoff structure:
99% chance: payoff of 0 1% chance: payoff of 1000
Clearly, E(X) is 10. However, gamblers like this form of bet, and are prepared to pay for it. Consequently, they are willing to bid up the price of X to (say) 11.
Y is the instrument formed by shorting X. When X is priced at 11, this has the following payoff structure:
99% chance: payoff of 11 1% chance: payoff of −989
Clearly, E(Y) is 1. In other words, you can make money, in expectation, by shorting X. However, there is a lot of downside risk here, and normals do not want to take it on. They would require E(Y) to be 2 (say) in order to take on a bet of that structure.
So, assuming you have a “normal” attitude to risk, you can lose money here (by buying X), but you can’t win it in risk-adjusted terms. This is caused by the market segmentation caused by the different risk profiles. Nothing here is contrary to the EMH, although it is contrary to the CAPM.
Thoughts:
Penny stocks (and high-beta instruments generally, such as deep out-of-the-money options) display this behaviour in real life.
A more realistic model might include some deep-pocketed funds with a neutral attitude to risk who could afford to short X. But in real life, there is market segmentation and a lack of liquidity. Penny stocks are illiquid and hard to short, and so are many other high-beta instruments.
The logical corollary of this model is that safe, boring equities will outperform stocks with lottery-ticket-like qualities. And it therefore follows that safe, boring equities will outperform the market as a whole. And that also seems true in real life.
There are plausible microfoundations for why there might be a “gambler” class of investor. For example, fund managers are risking their clients’ capital, not their own, and are typically paid in a ranking relative to their peers. Their incentives may well lead them to buy lottery tickets.
By itself, no. But this is diversifiable risk and so if you short enough penny stocks, the risk becomes acceptable. To use a historical example, realizing this (in the context of junk bonds) is what made Michael Milken rich. For a while, at least.
This certainly exists, though it’s more complicated than just unwillingness to touch skewed and heavy-tailed securities.
In real life shorting penny stocks will run into some transaction-costs and availability-to-borrow difficulties, but options are contracts and you can write whatever options you want. So are you saying that selling deep OOM options is a free lunch?
As for the rest, you are effectively arguing that EMH is wrong :-)
Full disclosure: I am not a fan of EMH.
Who says this risk is diversifiable? Nothing in the toy model I gave you said the risk was diversifiable. Maybe all the X-like instruments are correlated.
No, I’m not saying that selling deep OOM options is a free lunch, because of the risk profile. And these are definitely not diversifiable.
I am not arguing that EMH is wrong. I have given you a toy model, where a suitably defined investor cannot make money but can lose money. The model is entirely consistent with the EMH, because all prices reflect and incorporate all relevant information.
Oh, I thought we were talking about reality. EMH claims to describe reality, doesn’t it?
As to toy models, if I get to define what classes of investors exist and what do they do, I can demonstrate pretty much anything. Of course it’s possible to set up a world where “a suitably defined investor cannot make money but can lose money”.
And deep OOM options are diversifiable—there is a great deal of different markets in the world.
Yeah, but you wanted “a scenario where everything is happening pre-tax, there are no transaction costs, we’re operating in risk-adjusted terms and, to make things simple, the risk-free rate is zero. Moreover, the markets are orderly and liquid.” That doesn’t describe reality, so describing events in your scenario necessitates a toy model.
In the real world, it is trivial to show how you can lose money even if the EMH is true: you have to pay tax, transaction costs are non-zero, the ex post risk is not known, etc.
There’s still a lot of correlation. Selling deep OOM options and then running into unexpected correlation is exactly how LTCM went bust. It’s called “picking up pennies in front of a steamroller” for a reason.
Fair point :-) But still, with enough degrees of freedom in the toy model, the task becomes easy and so uninteresting.
I know. Which means you need proper risk management and capitalization. LTCM died because it was overleveraged and could not meet the margin calls. And LTCM relied on hedges, not on diversification.
Since deep OOM options are traded, there are people who write them. Since they are still writing them, it looks like not a bad business :-)
Yes. Unless you think that all possible market information is reflected now, before it becomes available, someone makes money when information emerges, moving the market.
Yes, you can (theoretically) make money by front-running the market. But I don’t think you can systematically lose money that way (and stay within EMH) and that’s the question under discussion.
If someone is making money by front-running the market another person at the other side of the trade is losing money.
We’re talking about ways to systematically lose money, which means you would need to systematically throw yourself into the front-runner’s path, which means you would know where that path is, which means you can systematically forecast the front-running. I think the EMH would be a bit upset by that :-)
Simply making random trades in a market where some participants are front runners will mean that some of those trades are with front runners where you lose money.
I would call that systematically losing money. On the other hand it doesn’t give you an ability to forcast where you will lose the money to make the opposite bet and win money.
Do you think our disagreement is about the way the EMH is defined or are you pointing to something more substantial?
No, no disagreement about EMH, that’s exactly the point.
It seems you shouldn’t be able to, since if you had such a system you could use the complement strategy (buy everything else) and make money.
You imply that the market is zero-sum. Some markets are, but a lot are not.
Correction: You would beat the market.
No, because you can’t sell what you don’t have.
In the financial markets you can, easily enough.
Sort of. You have to pay someone additional money for the right/ability to do so.
You have to pay a broker to sell what you have as well :-P
A lot less.
Also, this further breaks the asymmetry between making and loosing money.
I think you’re mistaken about that. As an empirical fact, it depends. What you are missing is the mechanism where when you sell a stock short, you don’t get to withdraw the cash (for obvious reasons). The broker keeps it until you cover your short and basically pays you interest on the cash deposit. Right now in most of the first world it’s miniscule because money is very cheap, that that is not the case always or everywhere.
It is perfectly possible to short a stock, cover it at exactly the same price and end up with more money in your account.
Actually, when you short a stock, you must pay an interest rate to the person from whom you borrowed the stock. That interest rate varies from stock to stock, but is always above the risk-free rate. Thus, if you short a stock and do nothing interesting with the cash and eventually cover it at the original price, you will lose money.
If you enter into a short sale at time 0 and cover at time T, you get paid interest on your collateral or margin requirement by the lender of the asset. This is called the short rebate or (in the bond market) the repo rate. As the short seller, you’ll be required to pay the time T asset price along with lease rate, which is based on the dividends or bond coupons the asset pays out from 0 to T.
So, if no dividends/coupons are paid out, it’s theoretically possible for you to profit from selling short despite no change in the underlying asset price.
The lease rate is an interest rate (ie, based on time) in addition to the absolute minimum payment of the dividends issued. It is set by the market: there is a limited supply of shares available to be borrowed for shorting. For most stocks it is about 0.3% for institutional investors, but 5% for a tenth of stocks. The point is that this is an asymmetry with buying a stock.
Now that I look it up and see that it is 0.3%, I admit that is not so big, but I think it is larger than the repo rate. I see no reason for the lease rate to be related to inflation, so in a high inflation environment, you could make money by shorting a stock that did not change nominal price.
(Dividends are not a big deal in shorting because the price of a stock usually drops by the amount of the dividend, for obvious reasons.)
Maybe if you have the right connections, and the broker really trust you. The issue is suppose you short a stock, the price goes up and you can’t cover it. Someone has to assume that risk, and of course will want a risk premium for doing so.
It doesn’t have anything to do with connections or broker trust. It’s standard operating practice for all broker clients.
If the price goes sufficiently up, you get a margin call. If you can’t meet it, the broker buys the stock to cover using the money in your account without waiting for your consent. The broker has some risk if the stock gaps (that is, the price moves discontinuously, it jumps directly from, say, $20 to $40), but that’s part of the risk the broker normally takes.
Another thing to watch out for when shorting stocks is dividends. If you are short a stock on the ex dividend date, then you have to pay the dividend on each share that you have shorted. However, as long as you keep margin calls and dividends in mind, short selling is a good technique (and an easy one) to play a stock that you are bearish on.
And, no, you don’t need any special connections, although you typically need to request short-selling privileges on your brokerage account.
Another way to play a stock you are bearish on is buying put options. But put options are a lot harder to use effectively because (among other reasons) they become worthless on the expiration date.
No because of taxes, transaction cost, and risk/return issues.
Yes, for strategies with low enough transaction costs (i.e. for most buy-and-hold like strategies, but not day-trading).
It will be somewhat hard for ordinary investors to implement the inverse strategies, since brokers that cater to them restrict which stocks they can sell short (professional investors usually don’t face this problem).
The EMH is only a loose approximation to reality, so it’s not hard to find strategies that underperform on average by something like 5% per year.
The EMH works because everybody is trying to gain money, so everybody except you trying to gain money and you trying to lose money isn’t the symmetric situation. The symmetric situation is everybody trying to lose money, in which case it’d be pretty hard indeed to do so. And if everybody except you was trying to lose money and you were trying to gain money it’d be pretty easy for you to do so. I think this would also be the case in absence of taxes and transaction costs. IOW I think Viliam nailed it and other people got red herrings.
Hugely important to distinguish between investing and trading here. But the short answer is that it’d be near impossible to lose money systematically without knowing the inverse (more profitable) strategy.
Consider the scenario where a 22-year-old teacher named Warren, who knows nothing about finance, takes 80% of his annual salary and buys random stocks with the intent to hold until retirement age (reinvesting all dividends). It would be extraordinarily fluky for him to not make solid returns over the long-run with this approach, let alone break even or lose money, as all publicly traded stocks have reasonably high positive expected value.
Now consider derivatives trading. Even if we assume no transaction costs, it’d be near-impossible for Warren to not lose money over the long-run by partaking in lots of random bets with, at best, 0 expected value. Your term, “the market” is problematic because “the market” can act as a bank or a poker table depending on the purchases of the investor.
EMH implies that it’s not easy to make a living through financial trading. It’s incredibly easy to slowly leak money to those who are making a living at it, though. Unlike buying stocks, bonds, etc., financial trading is zero-sum.