Short-term robots and long-term investors in the stock market
Consider the price history to be the sum of short term movements and long term movements. If you hold a stock for a long time you will benefit (or lose) from its long term movement.  If a sufficiently large and very good short term trader existed he would tend to reduce short term volatility, eventually to nearly zero. At that point, the price would rise gently over the course of the day in line with the long term variation in price. Presumably robot traders will increase the time horizon of their trades when they have exhausted the gains they can make from short term trades. "....causes loses [sic] to others. Someone sells you a stock.  The seller receives cash.  You receive a stock certificate.  This doesn't imply a loss by either party especially if the seller sold the stock for more than his purchase price. A day trading robot can make money off of the price changes of a stock only if there are buyers and sellers of the stock at certain prices.  There are always two parties in any stock transaction: a buyer and a seller.  The day trading robot can make money off of an investment for 20 years and you could still make money if the investment goes up over the 20 years.  The day trading robot doesn't ""rob"" you of any profit."
"If markets are efficient they will be unpredictable.  If all past information is already priced into a stock then movement will only occur when new information is introduced.  Since no one can predict future events stocks will move in an unpredictable way.  If markets are inefficient in the short term, people should be able to figure out the long-term price movements.  This doesn't seem to be the case.  This is why the authoritative book on market efficiency is called ""A **Random** Walk Down Wall Street""." How do we define worth? To stock traders and some investors it has value either as a transaction or as a piece in an asset allocation strategy. Is is likely to generate long term revenues and profits that reflect the historical relationship between those factors and stock price performance? Unlikely.  It might be a good short term play for the nimble investor but the real test of 'worth' will be after the initial hype dies down. It is what happens to the stock 90 days after it goes public that matters for the long term. Forgetting contributions to society, knowledge and culture, the markets will at that point make their determination about value. Here's how capital gains are totaled: Long and Short Term. Capital gains and losses are either long-term or   short-term. It depends on how long the taxpayer holds the property. If   the taxpayer holds it for one year or less, the gain or loss is   short-term. Net Capital Gain.  If a taxpayer’s long-term gains are more than their   long-term losses, the difference between the two is a net long-term   capital gain. If the net long-term capital gain is more than the net   short-term capital loss, the taxpayer has a net capital gain. So your net long-term gains (from all investments, through all brokers) are offset by any net short-term loss.  Short term gains are taxed separately at a higher rate. I'm trying to avoid realizing a long term capital gain, but at the same time trade the stock. If you close in the next year, one of two things will happen - either the stock will go down, and you'll have short-term gains on the short, or the stock will go up, and you'll have short-term losses on the short that will offset the gains on the stock.  So I don;t see how it reduces your tax liability.  At best it defers it. "Many investors don't invest for the short term and so a stock ""nose-diving"" in the short run will not affect their long term strategy so they will simply hold on to it until it recovers. Additionally funds that track an index have to hold on to the constituents of that index no matter what happens to its value over the period (within trading limits). Both of these kinds of investors will be able to lend stock in a company out and not trigger a forced buy-in on a short term change. If the underlying long-term health of the company changes or it is removed from indices it is likely that this will change, however. Employee stock plans and other investors who are linked directly to the company or who have a vested interest in the company other than in a financial way will also be unwilling (or unable) to sell on a down turn in the company. They will similarly be able to lend their stock in the short term." Your question reminds me of a Will Rogers quote: buy some good stock, and hold it till it goes up, then sell it. If it don’t go up, don’t buy it. There's no way to prevent yourself from buying a stock that goes down.  In fact all stocks go down at some times.  The way to protect your long term investment is to diversify, which increases the chances that you have more stocks that go up than go down.  So many advisors will encourage index funds, which have a low cost (which eats away at returns) and low rick (because of diversification).  If you want to experiment with your criteria that's great, and I wish you luck, but  Note that historically, very few managed funds (meaning funds that actively buy and sell stocks based on some set of criteria) outperform the market over long periods.  So don't be afraid of some of your stocks losing - if you diversify enough, then statistically you should have more winners than losers. It's like playing blackjack.  The goal is not to win every hand. The goal is to have more winning hands than losing hands. I remember like 20 years ago someone did an experiment where Peter Lynch, elementary school kids, and an ape, all picked stocks in a situation similar to this. The result was almost the same, with the elementary school kids coming out slightly better  Picking correct stocks is a craps shoot, as the market is an emotional entity, and in the short run, even educated guesses don't give an edge. People like Peter Lynch eventually win of course because of discipline, long term goals, and knowledge of tools like derivatives "Largely, because stock markets are efficient markets, at least mostly if not entirely; while the efficient market hypothesis is not necessarily 100% correct, for the majority of traders it's unlikely that you could (on the long term) find significant market inefficiencies with the tools available to an individual of normal wealth (say, < $500k). That's what frequent trading intends to do: find market inefficiencies.  If the market is efficient, then a stock is priced exactly at what it should be worth, based on risk and future returns.  If it is inefficient, then you can make more money trading on that inefficiency versus simply holding it long.  But in stating that a stock is inefficient, you are stating that you know something the rest of the market doesn't - or some condition is different for you than the other million or so people in the market.  That's including a lot of folks who do this for a living, and have very expensive modelling software (and hardware to run it on).  I like to think that I'm smarter than the far majority of people, but I'm probably not the smartest guy in the room, and I certainly don't have that kind of equipment - especially with high frequency trading nowadays. As such, it's certainly possible to make a bit of money as a trader versus as a long-term investor, but on the whole it's similar to playing poker for a living.  If you're smarter than most of the people in the room, you might be able to make a bit of money, but the overhead - in the case of poker, the money the house charges for the game, in the case of stocks, the exchange fees and broker commissions - means that it's a losing game for the group as a whole, and not very many people can actually make money.  Add to that the computer-based trading - so imagine a poker game where four of the eight players are computer models that are really good (and actively maintained by very smart traders) and you can see where it gets to be very difficult to trade at a profit (versus long term investments, which take advantage of the growth in value in the company). Finally, the risk because of leverage and option trading (which is necessary to really take advantage of inefficiencies) makes it not only hard to make a profit, but easy to lose everything.  Again to the poker analogy, the guys I've known playing poker for a living do it by playing 10-20 games at once - because one game isn't efficient enough, you wouldn't make enough money.  In poker, you can do that fairly safely, especially in limit games; but in the market, if you're leveraging your money you risk losing a lot.  Every action you take to make it ""safer"" removes some of your profit." "'Buy and Hold' Is Still a Winner: An investor who used index funds and stayed the course could have earned satisfactory returns even during the first decade of the 21st century. by By Burton G. Malkiel in The Wall Street Journal on November 18, 2010: ""The other useful technique is ""rebalancing,"" keeping the portfolio asset allocation consistent with the investor's risk tolerance. For example, suppose an investor was most comfortable choosing an initial allocation of 60% equities, 40% bonds. As stock and bond prices change, these proportions will change as well. Rebalancing involves selling some of the asset class whose share is above the desired allocation and putting the money into the other asset class. From 1996 through 1999, annually rebalancing such a portfolio improved its return by 1 and 1/3 percentage points per year versus a strategy of making no changes."" Mr. Malkiel is a professor of economics at Princeton University. This op-ed was adapted from the upcoming 10th edition of his book ""A Random Walk Down Wall Street,"" out in December by W.W. Norton. http://online.wsj.com/article/SB10001424052748703848204575608623469465624.html"