Why buying an inverse ETF does not give same results as shorting the ETF
Suppose that the ETF is currently at a price of $100.  Suppose that the next day it moves up 10% (to a price of $110) and the following day it moves down 5% (to a price of $104.5).  Over these two days the ETF has had a net gain of 4.5% from its original price. The inverse ETF reverses the daily gains/losses of the base ETF.  Suppose for simplicity that the inverse ETF also starts out at a price of $100.  So on the first day it goes down 10% (to $90) and on the second day it goes up 5% (to $94.5).  Thus over the two days the inverse ETF has had a net loss of 5.5%. The specific dollar amounts do not matter here.  The result is that the ETF winds up at 110%*95% = 104.5% of its original price and the inverse ETF is at 90%*105% = 94.5% of its original price.  A similar example is given here. As suggested by your quote, this is due to compounding.  A gain of X% followed by a loss of Y% (compounded on the gain) is not in general the same as a loss of X% followed by a gain of Y% (compounded on the loss).  Or, more simply put, if something loses 10% of its value and then gains 10% of its new value, it will not return to its original value, because the 10% it gained was 10% of its decreased value, so it's not enough to bring it all the way back up.  Likewise if it gains 10% and then loses 10%, it will go slightly below its original value (since it lost 10% of its newly increased value). "The most fundamental answer is that when you short a stock (or an ETF), you short a specific number of shares on a specific day, and you probably don't adjust this much as the price wobbles goes up and down. But an inverse fund is not tied to a specific start date, like your own transaction is.  It adjusts on an ongoing basis to maintain its full specified leverage at all times.  If the underlying index goes up, it has to effectively ""buy in"" because its collateral is no longer sufficient to support its open position.  On the other hand, if the underlying index goes down, that frees up collateral which is used to effectively short-sell more of the underlying.  So by design it will buy high and sell low, and so any volatility will pump money out of the fund. I say ""effectively"" because inverse funds use derivatives and contracts, rather than actually shorting the underlying security.   Which brings up the less fundamental issue.  These derivatives and contracts are relatively opaque; the counter-parties are in it for their own benefit, not yours; and the people who run the fund get their expenses regardless of how you do, and they are hard for you to monitor.  This is a hazardous combination."
Michael gave a good answer describing the transaction but I wanted to follow up on your questions about the lender. First, the lender does charge interest on the borrowed securities. The amount of interest can vary based on a number of factors, such as who is borrowing, how much are they borrowing, and what stock are they trying to borrow.  Occasionally when you are trying to short a stock you will get an error that it is hard to borrow. This could be for a few reasons, such as there are already a large amount of people who have shorted your broker's shares, or your broker never acquired the shares to begin with (which usually only happens on very small stocks). In both cases the broker/lender doesnt have enough shares and may be unwilling to get more. In that way they are discriminating on what they lend. If a company is about to go bankrupt and a lender doesnt have any more shares to lend out, it is unlikely they will purchase more as they stand to lose a lot and gain very little.  It might seem like lending is a risky business but think of it as occurring over decades and not months. General Motors had been around for 100 years before it went bankrupt, so any lender who had owned and been lending out GM shares for a fraction of that time likely still profited.  Also this is all very simplified. JoeTaxpayer alluded to this in the comments but in actuality who is lending stock or even who owns stock is much more complicated and probably doesnt need to be explained here. I just wanted to show in this over-simplified explanation that lending is not as risky as it may first seem. In addition to the higher risk as pointed out by @JamesRoth, you also need to consider that there are regulations against 'naked shorting' so you generally need to either own the security, or have someone that is willing to 'loan' the security to you in order to sell short.  If you own a stock you are shorting, the IRS could view the transaction as a Sell followed by a buy taking place in a less than 30 day period and you could be subject to wash-sale rules.  This added complexity (most often the finding of someone to loan you the security you are shorting) is another reason such trades are considered more advanced. You should also be aware that there are currently a number of proposals to re-instate the 'uptick rule' or some circuit-breaker variant. Designed to prevent short-sellers from driving down the price of a stock (and conducting 'bear raids etc) the first requires that a stock trade at the same or higher price as prior trades before you can submit a short.  In the latter shorting would be prohibited after a stock price had fallen a given percentage in a given amount of time.  In either case, should such a rule be (re)established then you could face limitations attempting to execute a short which you would not need to worry about doing simple buys or sells.   As to vehicles that would do this kind of thing (if you are convinced we are in a bear market and willing to take the risk) there are a number of ETF's classified as 'Inverse Exchange Traded Funds (ETF's) for a variety of markets that via various means seek to deliver a return similar to that of 'shorting the market' in question.  One such example for a common broad market is ticker SH the ProShares Short S&P500 ETF, which seeks to deliver a return that is the inverse of the S&P500 (and as would be predicted based on the roughly +15% performance of the S&P500 over the last 12 months, SH is down roughly -15% over the same period).  The Wikipedia article on inverse ETF's lists a number of other such funds covering various markets.   I think it should be noted that using such a vehicle is a pretty 'aggressive bet' to take in reaction to the belief that a bear market is imminent.  A more conservative approach would be to simply take money out of the market and place it in something like CD's or Treasury instruments.  In that case, you preserve your capital, regardless of what happens in the market. Using an inverse ETF OTOH means that if the market went bull instead of bear, you would lose money instead of merely holding your position. "Depends on how far down the market is heading, how certain you are that it is going that way, when you think it will fall, and how risk-averse you are.  By ""better"" I will assume you are trying to make the most money with this information that you can given your available capital. If you are very certain, the way that makes the most money for the least investment from the options you provided is a put.  If you can borrow some money to buy even more puts, you will make even more.  Use your knowledge of how far and when the market will fall to determine which put is optimal at today's prices.  But remember that if the market stays flat or goes up you lose everything you put in and may owe extra to your creditor.  A short position in a futures contract is also an easy way to get extreme leverage.  The extremity of the leverage will depend on how much margin is required.  Futures trade in large denominations, so think about how much you are able to put to risk. The inverse ETFs are less risky and offer less reward than the derivative contracts above.  The levered one has twice the risk and something like twice the reward.  You can buy those without a margin account in a regular cash brokerage, so they are easier in that respect and the transactions cost will likely be lower. Directly short selling an ETF or stock is another option that is reasonably accessible and only moderately risky.  On par with the inverse ETFs." You can't make money on the way down if it was your money that bought the shares when the market was up.  When you sell short, borrowing lets you tap into the value without paying for it. That way, when the price (hopefully) drops you profit from the difference. In your example, if you hadn't paid the £20 in the first place, then you would actually be up £5. But since you started with £20, you still show loss. As others said, borrowing is the definition of selling short. It is also simply the only way the math works. Of course, there is a large risk you must assume to enjoy benefiting from something you do not own! It's actually quite simple. You're actually confusing two concept. Which are taking a short position and short selling itself. Basically when taking a short position is by believing that the stock is going to drop and you sell it. You can or not buy it back later depending on the believe it grows again or not. So basically you didn't make any profit with the drop in the price's value but you didn't lose money either.  Ok but what if you believe the market or specific company is going to drop and you want to profit on it while it's dropping. You can't do this by buying stock because you would be going long right? So back to the basics. To obtain any type of profit I need to buy low and sell high, right? This is natural for use in long positions. Well, now knowing that you can sell high at the current moment and buy low in the future what do you do? You can't sell what you don't have. So acquire it. Ask someone to lend it to you for some time and sell it. So selling high, check.  Now buying low? You promised the person you would return him his stock, as it's intangible he won't even notice it's a different unit, so you buy low and return the lender his stock. Thus you bought low and sold high, meaning having a profit. So technically short selling is a type of short position. If you have multiple portfolios and lend yourself (i.e. maintaining a long-term long position while making some money with a short term short-term strategy) you're actually short selling with your own stock. This happens often in hedge funds where multiple strategies are used and to optimise the transaction costs and borrowing fees, they have algorithms that clear (match) long and short coming in from different traders, algorithms, etc. Keep in mind that you while have a opportunities risk associated.  So basically, yes, you need to always 'borrow' a product to be able to short sell it. What can happen is that you lend yourself but this only makes sense if: This is dumb on many levels.  First are they really trying to blame the Flash Crash for investors leaving the market. It's 2014 and they claim in 17 of 25 months since the 2010 crash investors have withdrawn (not really sure what this means either, since shares don't disappear- does this just mean the market is up? It's unclear). Either way the article quoted is from 2012! And for a research team creating an empirical model, this is a very scary usage of small sample size,  mistaking correlation for causation,  etc.  And the algo,  though they don't give much info,  seems to be the very essence of data mining. Pick a million signals and filter on those that are empirically the best.  If you are an individual investor or a small fund thinking of purchasing something like this,  first consider: if it really worked, why are the founders selling it when they could just use it themselves and profit from it? It's almost guaranteed not to work out of sample I have heard of this, but then the broker is short the shares if they weren't selling them out of inventory, so they still want to accumulate the shares or a hedge before EOD most likely - In that case it may not be the client themselves, but that demand is hitting the market at some point if there isn't sufficient selling volume.    Whether or not the broker ends up getting all of them below VWAP is a cost of marketing for them, how they expect to reliably get real size below vwap is my question. They're exchange traded debt, basically, not funds. E.g. from the NYSE: An exchange-traded note (ETN) is a senior unsecured debt obligation designed to track the total return of an underlying market index or other benchmark, minus investor fees. Whereas an ETF, in some way or another, is an equity product - which doesn't mean that they can only expose you to equity, but that they themselves are a company that you buy shares in.  FCOR for example is a bond ETF, basically a company whose sole purpose is to own a basket of bonds.  Contrast that to DTYS, a bear Treasury ETN, which is described as  The ETNs are unsecured debt obligations of the issuer, Barclays Bank PLC, and are not, either directly or indirectly, an obligation of or guaranteed by any third party. Also from Barclays site: Because the iPath ETNs are debt securities, they do not have any voting rights. FCOR on the other hand is some sort of company owned/managed by a Fidelity trust, though my EDGAR skills are rusty. AGREEMENT made this 18th day of   September, 2014, by and between Fidelity Merrimack Street Trust, a Massachusetts business trust which may issue one or more series of shares of beneficial interest (hereinafter called the Trust), on behalf of Fidelity Corporate   Bond ETF (hereinafter called the Fund), and Fidelity Investments Money Management, Inc., a New Hampshire corporation (hereinafter called the Adviser) as set forth in its entirety below. The ETF supply management policy is arcane.  ETFs are not allowed to directly arbitrage their holdings against the market.  Other firms must handle redemptions & deposits.  This makes ETFs slightly costlier than the assets held. For ETFs with liquid holdings, its price will rarely vary relative to the holdings, slippage of the ETF's holdings management notwithstanding.  This is because the firms responsible for depositing & redeeming will arbitrage their equivalent holdings of the ETF assets' prices with the ETF price. For ETFs with illiquid holdings, such as emerging markets, the ETF can vary between trades of the holdings.  This will present sometimes large variations between the last price of the ETF vs the last prices of its holdings. If an ETF is shunned, its supply of holdings will simply drop and vice versa. The risk of the particular share moving up or down is same for both.   however in terms of mitigating the risk, Investor A is conservative on upside, ie will exit if he gets 10%, while is ready to take unlimited downside ... his belief is that things will not go worse .. While Investor B is wants to make at least 10% less than peak value and in general is less risk averse as he will sell his position the moment the price hits 10% less than max [peak value] So it more like how do you mitigate a risk, as to which one is wise depends on your belief and the loss appetite There are rules that prevent two of the reactive measures you suggest from occurring. First, on the date of and shortly following an IPO, there is no stock available to borrow for shorting. Second, there are no put options available for purchase. At least, none that are listed, of the sort you probably have in mind. In fact, within a day or two of the LinkedIn IPO, most (all?) of the active equity traders I know were bemoaning the fact that they couldn't yet do exactly what you described i.e. buying puts, or finding shares to sell short. There was a great deal of conviction that LinkedIn shares were overpriced, but scant means available to translate that market assessment into an influence of market value. This does not mean that the Efficient Markets Hypothesis is deficient. Equilibrium is reached quickly enough, once the market is able to clear as usual. SeekingAlpha has a section dedicated to Short ETFs as well as others. In there you will find SH, and SDS.  Both of which are inverse to the S&P 500.  Edit: I linked to charts that compare SH and SDS to SPY. The product type and transaction direction are not linked.  When you short sell a stock, you are still dealing with shares of an equity security.  When you take delivery of a bond, you are buying that bond and holding a long position even though it's a debt security. There is no margin call. Inverse ETFs use derivatives that would lose value in the case you describe though this doesn't force a margin call as you may be misunderstanding how these funds are constructed. It's not quite identical, due to fees, stock rights, and reporting & tax obligations.  But the primary difference is that a person could have voting rights in a company while maintaining zero economic exposure to the company, sometimes known as empty voting. As an abstract matter, it's identical in that you reduce your financial exposure whether you sell your stock or short it.  So the essence of your question is fundamentally true.  But the details make it different.  Of course there are fee differences in how your broker will handle it, and also margin requirements for shorting.  Somebody playing games with overlapping features of ownership, sales, and purchases, may have tax and reporting obligations for straddles, wash sales, and related issues.  A straight sale is generally less complicated for tax reporting purposes, and a loss is more likely to be respected than someone playing games with sales and purchases. But the empty voting issue is an important difference.  You could buy stock with rights such as voting, engage in other behavior such as forwards, shorts, or options to negate your economic exposure to the stock, while maintaining the right to vote.  Of course in some cases this may have to be disclosed or may be covered by contract, and most people engaging in stock trades are unlikely to have meaningful voting power in a public company.  But the principle is still there. As explained in the article by Henry Hu and Bernie Black: Hedge funds have been especially creative in decoupling voting rights from economic ownership. Sometimes they hold more votes than economic ownership - a pattern we call empty voting. In an extreme situation, a vote holder can have a negative economic interest and, thus, an incentive to vote in ways that reduce the company's share price. Sometimes investors hold more economic ownership than votes, though often with morphable voting rights - the de facto ability to acquire the votes if needed. We call this situation hidden (morphable) ownership because the economic ownership and (de facto) voting ownership are often not disclosed.