Somewhat along the lines of this question. I've been putting mostly unmatched money into my 401(k) for a few years. I know that investing is generally seen as a long-term decision, but with volatile stocks, it seems to me that you could make a large amount of money by buying low and selling high just a few months later. I also know I'm far from the first person to think this and there's probably a technical term for this practice.

I was looking at some charts and it seems a lot of companies' stock prices have gone down significantly since around October, which correlates with the market scare around that time. If they return to their earlier prices, I could make 20-50% in a short amount of time, and repeat that each time a company goes into a slump. Assuming I don't make too many poor choices, what incentive do I have to invest in relatively stable companies over a long period of time vs. volatile stocks for a few months? Why is this quick-buy-quick-sell-quick-win generally not seen as a good or sensible practice?

Edit: To make this quick buying and selling possible, I would adopt a guideline of "sell when you've made X%, even if it looks like it might go higher." Holding the stock for a longer period of time to see how it continues to do is precisely the practice that I'm challenging in this question.

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    Timing the market is extremely difficult.
    – TainToTain
    Commented Dec 3, 2015 at 4:27
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    You say: "Assuming I don't make too many poor choices..." Then: "Why is this quick-buy-quick-sell-quick-win generally not seen as a good or sensible practice?" You just answered your own question.
    – BrenBarn
    Commented Dec 3, 2015 at 5:05
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    Obligatory Will Rogers quote: "Don't gamble; take all your savings and buy some good stock and hold it till it goes up, then sell it. If it don't go up, don't buy it." Commented Dec 3, 2015 at 12:20
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    What leads you to believe you wouldn't instead end up buying high and selling low, for quick, big losses?
    – T.E.D.
    Commented Dec 3, 2015 at 14:29
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    "Buy low and sell high" is exactly as good of advice for a trader as "pick good numbers is" for someone buying lottery tickets, and for the same basic reason. Commented Dec 3, 2015 at 15:07

15 Answers 15


There are people (well, companies) who make money doing roughly what you describe, but not exactly. They're called "market makers". Their value for X% is somewhere on the scale of 1% (that is to say: a scale at which almost everything is "volatile"), but they use leverage, shorting and hedging to complicate things to the point where it's nothing like a simple as making a 1% profit every time they trade. Their actions tend to reduce volatility and increase liquidity.

The reason you can't do this is that you don't have enough capital to do what market makers do, and you don't receive any advantages that the exchange might offer to official market makers in return for them contracting to always make both buy bids and sell offers (at different prices, hence the "bid-offer spread"). They have to be able to cover large short-term losses on individual stocks, but when the stock doesn't move too much they do make profits from the spread.

The reason you can't just buy a lot of volatile stocks "assuming I don't make too many poor choices", is that the reason the stocks are volatile is that nobody knows which ones are the good choices and which ones are the poor choices. So if you buy volatile stocks then you will buy a bunch of losers, so what's your strategy for ensuring there aren't "too many"? Supposing that you're going to hold 10 stocks, with 10% of your money in each, what do you do the first time all 10 of them fall the day after you bought them? Or maybe not all 10, but suppose 75% of your holdings give no impression that they're going to hit your target any time soon. Do you just sit tight and stop trading until one of them hits your X% target (in which case you start to look a little bit more like a long-term investor after all), or are you tempted to change your strategy as the months and years roll by?

If you will eventually sell things at a loss to make cash available for new trades, then you cannot assess your strategy "as if" you always make an X% gain, since that isn't true. If you don't ever sell at a loss, then you'll inevitably sometimes have no cash to trade with through picking losers. The big practical question then is when that state of affairs persists, for how long, and whether it's in force when you want to spend the money on something other than investing.

So sure, if you used a short-term time machine to know in advance which volatile stocks are the good ones today, then it would be more profitable to day-trade those than it would be to invest for the long term. Investing on the assumption that you'll only pick short-term winners is basically the same as assuming you have that time machine ;-)

There are various strategies for analysing the market and trying to find ways to more modestly do what market makers do, which is to take profit from the inherent volatility of the market. The simple strategy you describe isn't complete and cannot be assessed since you don't say how to decide what to buy, but the selling strategy "sell as soon as I've made X% but not otherwise" can certainly be improved. If you're keen you can test a give strategy for yourself using historical share price data (or current share price data: run an imaginary account and see how you're doing in 12 months). When using historical data you have to be realistic about how you'd choose what stocks to buy each day, or else you're just cheating at solitaire. When using current data you have to beware that there might not be a major market slump in the next 12 months, in which case you won't know how your strategy performs under conditions that it inevitably will meet eventually if you run it for real. You also have to be sure in either case to factor in the transaction costs you'd be paying, and the fact that you're buying at the offer price and selling at the bid price, you can't trade at the headline mid-market price.

Finally, you have to consider that to do pure technical analysis as an individual, you are in effect competing against a bank that's camped on top of the exchange to get fastest possible access to trade, it has a supercomputer and a team of whizz-kids, and it's trying to find and extract the same opportunities you are. This is not to say the plucky underdog can't do well, but there are systematic reasons not to just assume you will. So folks investing for their retirement generally prefer a low-risk strategy that plays the averages and settles for taking long-term trends.

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    Can I upvote twice just this time, @stackExchange? Please? Commented Dec 3, 2015 at 18:59
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    Your suggestion to give a test with historical data reminded me of the Chart Game which explicitly does that.
    – Bobson
    Commented Dec 4, 2015 at 1:53

If they return to their earlier prices

Assuming I don't make too many poor choices

That's your problem right there: you have no guarantee that stocks, will in fact return to their earlier prices rather than go down some more after the time you buy them.

Your strategy only looks good and easy in hindsight when you know the exact point in time when stocks stopped going down and started going up. But to implement it, you need to predict that time, and that's impossible.

I would adopt a guideline of "sell when you've made X%, even if it looks like it might go higher."

Congratulations, you've come up with the concept of technical analysis. Now go and read the hundreds of books that have been written about it, then think about why the people who wrote them waste time doing so rather than getting rich by using that knowledge.

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    And furthermore, think about whether the people who can make money through technical analysis are writing books about it, or if they're getting jobs in the high-frequency trading departments of banks. Basically, if a retired multi-millionaire writes a book about technical analysis, then what they say might well be both true and effective when applied to the time period over which they made their fortune. Whether that's enough information for an individual investor to make a profit next week is quite another matter. Commented Dec 3, 2015 at 12:47
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    Anyone who writes a book telling you how to get rich is obviously getting rich by selling books, not following their own advice! (the one exception being people who write books telling you how to be an author)
    – gbjbaanb
    Commented Dec 3, 2015 at 15:21
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    @gbjbaanb ”How to get rich by writing books on how to get rich”.
    – gerrit
    Commented Dec 4, 2015 at 10:58
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    +1 "then think about why the people who wrote them waste time doing so rather than getting rich by using that knowledge" Commented Dec 6, 2015 at 15:52

On Black Friday, 1929,the market fell from over 350 to just above 200. If you were following your plan then you would buy in at about 200. But look what the market did for two years after Black Friday.

enter image description here

It went down to about 50. You would have lost around 75% of your capital.

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    Now look at what it did after that. There were jagged little local peaks and valleys everywhere a day trader could lose their shirt on. However, the long-term trend was that it went from under 50 to 250 over the next 20 years. If you just kept your investments there indexed to the average and left them alone for a couple of decades, you'd have made 400%. (Inflation over that entire period was about 100%)
    – T.E.D.
    Commented Dec 3, 2015 at 14:26
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    More millionaires were created during the Great Depression in America than at any other time. That graph shows why. Notice how the poster says "LOOK AT THIS DISASTER" but fails to tell you, it was only 3 years and you had 3 years to buy and own everything for pennies on the USD. I've never seen a post like this that refuted its own point. It's called perspective. Commented Dec 4, 2015 at 1:03
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    @user541852587 it doesn't refute it's own point... there were winners and losers. The OP's strategy can just as easily be a loser, that's the point. You can go write another post telling the OP it's a good idea because it'll work a good half the time if you want.
    – djechlin
    Commented Dec 4, 2015 at 4:22
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    @T.E.D. this question is about short term trading, not long term trading. Waiting 20 years sounds pretty long term to me.
    – NPSF3000
    Commented Dec 4, 2015 at 23:05
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    @T.E.D. to me the question is phrased as why shouldn't I do short term trading as opposed to why is long term trading better. A 400% ROI of 20 years while interesting, doesn't explain why not do short term.
    – NPSF3000
    Commented Dec 5, 2015 at 3:06

The technical term for it is "timing the market" and if you can pull it off correctly, you will do quite well. The problem is that it is almost impossible to consistently do well. If it were that easy there would be a lot of billionaires walking around. Even Wall street experts haven't been able to predict the market that well.

This idea is almost universally considered a bad idea.

Consider this: When has the stock dropped low enough that you are "buying low" and let's say you do buy low and it doubles in a month. When do you get out? What if you are wrong and it doubles again? Or if it drops 10% do you keep waiting? This strategy is rife with problems.

  • The question of when to sell high is valid and I forgot to address it in my original post. Say I set a flat goal of 50% gain, accepting the possibility that it could keep going up after I sell it. Does that make a difference in your answer?
    – Pedro
    Commented Dec 3, 2015 at 4:38
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    Not really. How do you know the stock won't plummet as soon as you buy it? Then what?
    – JohnFx
    Commented Dec 3, 2015 at 5:07
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    In my experience, statistically speaking, stocks are somewhat likely to plummet a few moments after I buy them. So I use my gut feelings about a stock as a partial contrarian indicator. :-)
    – user
    Commented Dec 4, 2015 at 9:48
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    The problem with "If it was easy to do, there would be many billionaires" is that the real economy doesn't sustain that. The actual objection is that the strategy would be self-defeating. If everybody knew which stocks are valuable, they would be expensive already. The key to "buy low sell high" is that there's a sucker willing to sell you those valuable stocks for pennies.
    – MSalters
    Commented Dec 4, 2015 at 10:44
  • @MSalters The other key to "buy low, sell high" not being sustainable is there's a sucker willing to buy those [about to be] valueless stocks for pennies. You generally cannot tell in advance which category a stock is in (has it slumped because of a knee-jerk reaction and will crawl back up; or has the slump killed the business-model or cash-flow and the company's about to go bust).
    – TripeHound
    Commented Dec 7, 2015 at 13:34

Every time you buy or sell a share for some price, somebody must have thought that that was exactly the right moment to sell or buy that share at that price (and to trade with you).

Every time a trade is made, both sides think they are doing the smart thing. Most of the time, one will turn out to be wrong, the other right.

Nothing in your proposed method of trading explains why you would be the side that was right more often. So they'll probably even out. Or maybe there are people in the market who actually do have a slightly better than average method, and you'll be wrong somewhat more often than right.

Each trade has transaction costs.

If you simply hang on to your shares, that's more or less the same as evening out good trades and bad trades, but without the transaction costs.

  • And one common scenario when both the buyer and the seller genuinely are right, is long-term investing. You're a 23-year-old who wants a nice retirement, so you buy Berkshire Hathaway because you think it'll grow basically for ever. I'm a 63-year-old who wants a boat, but 40 years ago I thought like you. I sell Berkshire Hathaway to you because I don't have forever. So, the reason for long-term investing is to wait until your correct decision to buy becomes a correct decision to sell. Commented Jan 29, 2021 at 20:55

The price of a shares reflects the expected future returns of that company. If it does not someone will notice and buy until it does. Look at this chart http://www.finanzen.net/chart/Arcandor (click on max), that's a former DAX company, so one of the largest german companys. Now it's bankrupt. Why do you think you are the only one who is going to notice? There are millions of people and even more computers, some a going to be smarter than you.

Of course that does not happen to everyone but who knows. Is Volkswagen going to survive the current crisis? Probably. Is it coming back to former glory in the next half year? Who knows?

Here comes the obvious solution: Don't buy single stocks, spread it out over many companies, some will shine, some will plument and you get the average. Oh that's an index, how convinent. Now if there were a way to save on all these transaction costs you're incurring...


As an easy way to answer... look at an index, let's say the S&P 500. Look at the price this last October, and predict where it will move in November... easy right? It already happened, and you have the benefit of hindsight. The move looks like such a consistent, obvious continuation of the previous up and down pattern. It looks predictable, like you could have guessed that.

Now, look at today's price, and predict where it will go next month. Not so easy now? The problem is, every point you're at, all the time, looks like a possible inflection point or turning point. If you're following an uptrend, you may think it'll continue, but you may also think that it zigged so far up already, that now it's ready for a zag down where you'll buy. So you wait... and it keeps rising, and you kick yourself for missing out. Next time, you see another uptrend and resolve to buy it regardless, thinking now it'll keep going, but it turns down the second you buy it, and keeps dropping. You kick yourself again. The market is amazing at doing this to you every time. In real time, every wiggle in the price looks simultaneously like a trend that could continue, and like a trend that has moved far enough and is ready to reverse. And more likely you'll guess the wrong one.

The ONLY way with some little hope of succeeding is to study study study, and find and learn trading rules with just over 50/50 chances (like buying when a moving average is touched within an uptrend as an example, and setting a stop loss at -1%, and a sell limit at +2% or something), and then never ever deviate from that strategy, because your only hope is in the consistency of statistics and odds over time. You'll get many -1% losses, and hopefully enough 2% gains to compensate the losses, plus some profit.

OR, to make it easier, just buy in on a dip, and hold and hold and collect dividends, and be content to match the market without effort.


The stock market's principal justification is matching investors with investment opportunities. That's only reasonably feasible with long-term investments. High frequency traders are not interested in investments, they are interested in buying cheap and selling expensive. Holding reasonably robust shares for longer binds their capital which is one reason the faster-paced business of dealing with options is popular instead. So their main manner of operation is leeching off actually occuring investments by letting the investors pay more than the recipients of the investments receive.

By now, the majority of stock market business is indirect and tries guessing where the money goes rather than where the business goes.

For one thing, this leads to the stock market's evaluations being largely inflated over the actual underlying committed deals happening. And as the commitment to an investment becomes rare, the market becomes more volatile and instable: it's money running in circles.

Fast trading is about running in front of where the money goes, anticipating the market. But if there is no actual market to anticipate, only people running before the imagination of other people running before money, the net payout converges to zero as the ratio of serious actual investments in tangible targets declines.

By and large, high frequency trading converges to a Ponzi scheme, and you try being among the winners of such a scheme. But there are a whole lot of people competing here, and essentially the net payoff is close to zero due to the large volumes in circulation as opposed to what ends up in actual tangible investments.

It's a completely different game with different rules riding on the original idea of a stock market. So you have to figure out what your money should be doing according to your plans.

  • HFT provides a great deal of liquidity in the market which consequently allows for tighter spreads and improved fills. The vast majority of shares are held by large companies of interest, mutual funds, and pension related funds. Commented Dec 5, 2015 at 15:58

Someone entering a casino with $15 could employ a very simple strategy and have a better-than-90% chance of walking out with $16. Unfortunately, the person would have a non-trivial chance (about one in 14) of walking out with $0.

If after losing $15 the person withdrew $240 from the bank and tried to win $16, the person would have a better-than-90% chance of succeeding and ending up ahead (holding the original $15, plus the additional $240, plus $1) but would have at that point about a one in 14 chance from that point of losing the $240 along with the original $15. Measured from the starting point, you'd have about a 199 out of 200 chance of gaining $1, and a one out of 200 chance of losing $240.

Market-timing bets are like that. You can arrange things so you have a significant chance of making a small profit, but at the risk of a large downside. If you haven't firmly decided exactly how much downside you are willing to accept, it's very easy to simultaneously believe you don't have much money at risk, but that you'll be able to win back anything you lose. The only way you can hope to win back anything you lose is by bringing a lot more money to the table, which will of course greatly increase your downside risk.

The probability of making money for the person willing to accept $15 of downside risk to earn $1 is about 93%. The probability of making money for the person willing to accept $255 worth of risk is about 99.5%. It's easy to see that there are ways of playing which have a 99.5% chance of winning, and that there are ways of playing that only have a 15:1 downside risk. Unfortunately, the ways of playing that have the smaller risk don't have anything near a 99.9% chance of winning, and those that have a better chance of winning have a much larger downside risk.

  • Add to that a 100% chance of paying transaction costs for every bet and it looks even worse.
    – user34634
    Commented Dec 7, 2015 at 13:33
  • @Godzillarissa: Casinos have a vig too; I assumed a roughly-1% vig for my examples. Craps charges less; many other games charge more. I think certain kinds of stock market merchant accounts may reduce the vig to below 1% in exchange for monthly or annual fees, but my key point was that the primary thing that makes such strategies seem attractive is that there are strategies which have zero risk of a large loss (if you enter with $15 and don't stake any of your own money beyond that, you'll never lose more than $15) and strategies with a very small risk of any loss (but...
    – supercat
    Commented Dec 7, 2015 at 16:52
  • ...which have a non-zero risk of a very large loss). If one isn't clear about how much money one is willing to risk, it's easy to simultaneously believe one has no risk of a large loss, but one will still be able to win back one's losses.
    – supercat
    Commented Dec 7, 2015 at 16:54

Plenty of good answers here, but probably the best answer is that The Market relies on suckers...er...investors like you. The money has to come from somewhere, it might as well be you.

So-called "day traders" or "short-term investors" are a huge part of the market, and they perform a vital function: they provide capital that flows to the large, well-equipped, institutional investors. Thing is, you can never be big enough, smart enough, well-informed enough, or quick enough to beat the big guys. You may have a run of good fortune, but over the long term aggregate, you're a PAYOR into the market, not a DIVIDEND reaper.

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    You speak of the market like it's some kind of evil force. It's not. It's composed of buyers and sellers - that's it. People tend to get hurt when they branch too far outside what they know; this even happens with stores like Walmart. One person may not recognize a deal that another person does. There is no "market force" screwing people over. Commented Dec 5, 2015 at 0:52
  • Of course it's not "evil." That would be ridiculous. It's just rapacious. It eats little tiny day-trading investors for breakfast. Not a value judgement, just an observation.
    – dwoz
    Commented Dec 5, 2015 at 1:39
  • quick note, Joe Taxpayer: the word is "payor," not "payer." not a typo.
    – dwoz
    Commented Dec 6, 2015 at 17:50

A lot of people have already explained that your assumptions are the issue, but I'll throw in my 2¢.

There are a lot of people who do the opposite of long term investing. It's called high frequency trading. I'd recommend reading the Wikipedia article for more info, but very basically, high frequency traders use programs to determine which stocks to buy and which ones to sell. An example program might be "buy if the stock is increasing and sell if I've held it more than 1 second."

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    Note that HFT is going to involve very large commissions. It will also require your computer (the one running the trading program) to have a very low-latency connection to the exchanges, because you'll be competing against all the other high frequency traders who will snipe you if you're too slow. If this interests you, it's probably more worthwhile to invest in a fund managed by someone who has the resources to do this with the fund's assets. Doing it yourself might be fun, but it's playing with massive amounts of fire.
    – David C.
    Commented Dec 4, 2015 at 19:09
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    @DavidC. Absolutely. I don't think it's a strategy worth "trying," but I do think it's an interesting thing to think about when learning about alternatives to long term investing Commented Dec 4, 2015 at 19:18

Playing the markets is simple...always look for the sucker in the room and outsmart him. Of course if you can't tell who that sucker is it's probably you. If the strategy you described could make you rich, cnbc staff would all be billionaires. There are no shortcuts, do your research and decide on a strategy then stick to it in all weather or until you find a better one.


The problem is that short-term trends are really unpredictable. There is nobody who can accurately predict where a fund (or even moreso, a single stock or bond) is going to move in a few hours, or days or even months.

The long-term trends of the entire market, however, are (more or less) predictable. There is a definite upward bias when you look at time-scales of 5, 10, 20 years and more. Individual stocks and bonds may crash, and different sectors perform differently from year to year, but the market as a whole has historically always risen over long time scales.

Of course, past performance never guarantees future performance. It is possible that everything could crash and never come back, but history shows that this would be incredibly unlikely. Which is the entire basis for strategies based on buying and holding (and periodically rebalancing) a portfolio containing funds that cover all market sectors.

Now, regarding your 401(k), you know your time horizon. The laws won't let you withdraw money without penalty until you reach retirement age - this might be 40 years, depending on your current age. So we're definitely talking long term. You shouldn't care about where the market goes over a few months if you won't be using the money until 20 years from now.

The most important thing for a 401(k) is to choose funds from those available to you that will be as diverse as possible. The actual allocation strategy is something you will need to work out with a financial advisor, since it will be different for every person. Once you come up with an appropriate allocation strategy, you will want to buy according to those ratios with every paycheck and rebalance your funds to those ratios whenever they start to drift away. And review the ratios with your advisor every few years, to keep them aligned with large-scale trends and changes in your life.


There are many technical answers above , but the short story to me is that very few active fund managers consistently beat the market. Look at the results of actively managed funds. Depending on whose analysis you read, you will find out that somewhere between 80-90% of fund managers in a given year do not beat passive index funds. So go figure how you will do compared to a mutual fund manager who has way more experience than you likely have.

So, that in itself is moderately interesting, but if you look at same-manager performance over several consecutive years it is rare to find anyone that goes beats the market for more than a few years in a row. There are exceptions, but go pick one of these guys/gals - good luck.

Getting in and out of the market is a loser. This is because there is no way to see market spikes and down turns. There are many behavioral studies that have been done that show people do the wrong thing: they sell after losses have occurred and they buy after the market has gone up. Missing an up spike and not being in before the spike is as devastating as missing a down turn and not getting out in time.

There is another down side, if you are trading in a personal account, rather than a tax deferred account, going in and out of stocks has tax complications.

In short, a broad based equity index will, over time, beat about anything out there and it will do it in a tax efficient manner.

Exchange traded funds (ETFs) are a wonderful way to obtain diversification immediately at very low cost.

  • I would suggest that part of the reason fund managers rarely beat the market, is that they are constrained in their asset mix, i.e. cant be in cash. or have to have a certain percentage of blue chips, etc.
    – Marcus D
    Commented Apr 26, 2016 at 12:11

Another benefit of holding shares longer was just pointed out in another question: donating appreciated shares to a nonprofit may avoid the capital gains tax on those shares, which is a bigger savings the more those shares have gone up since purchase.

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