Idea for getting rich using computers to track stocks
The main reason I'm aware of that very few individuals do this sort of trading is that you're not taking into account the transaction costs, which can and will be considerable for a small-time investor. Say your transaction costs you $12, that means in order to come out ahead you'll have to have a fairly large position in a given instrument to make that fee back and some money. Most smaller investors wouldn't really want to tie up 5-6 figures for a day on the chance that you'll get $100 back. The economics change for investment firms, especially market makers that get special low fees for being a market maker (ie, offering liquidity by quoting all the time). "I (and probably most considering trading) had a similar thought as you.  I thought if I just skimmed the peaks and sold before the troughs, perhaps aided by computer, I'd be able to make a 2% here, 2% there, and that would add up quickly to a nice amount of money.  It almost did seem ""foolproof"". Then I realized that sometimes a stock just slides...down...and there is no peak higher than what I bought it for.  ""That's OK,"" I'd think, ""I'm sure it will recover and surpass the price I bought it for...so now I play the waiting game.""  But then it continues sliding, and my $10k is now worth $7k.  Do I sell?  Did I build a stop loss point into my computer program?  If so, what is the right place to put that stop?  What if there is a freak dip down and it triggers the stop loss but THEN my stock recovers?  I just lost $14,000 like this last week--luckily, only virtually! The point is, your idea only has half a chance to work when there is a mildly volatile stock that stays around some stable baseline, and even then it is not easy.  And then you factor in fees as others mentioned... People do make money doing this (day traders), and some claim you can use technical analysis to time orders well, so if you want to try that, read about technical analysis on this site or elsewhere." "There are many ways to trade. Rules based trading is practiced by professionals. You can indeed create a rule set to make buy and sell decisions based on the price action of your chosen security. I will direct you to a good website to further your study: I have found that systemtradersuccess.com is a well written blog, informative and not just a big sales pitch. You will see how to develop and evaluate trading systems. If you decide to venture down this path, a good book to read is Charles Wright's ""Trading As A Business."" It will get a little technical, as it discusses how to develop trading systems using the Tradestation trading platform, which is a very powerful tool for advanced traders and comes with a significant monthly usage fee (~$99/mo). But you don't have to have tradestation to understand these concepts and with an intermediate level of spreadsheet skills, you can run your own backtests.  Here is a trading system example, Larry Connors' ""2 period RSI system"", see how it is evaluated: http://systemtradersuccess.com/connors-2-period-rsi-update-2014/, and this video teaches a bit more about this particular trading system: https://www.youtube.com/watch?v=i_h9P8dqN4Y IMPORTANT: This is not a recommendation to use this or any specific trading system, nor is it a suggestion that using these tools or websites is a path to guaranteed profits. Trading is a very risky endeavor. You can easily lose huge sums of money. Good luck!"
"First, let me answer the question the best way I can: I don't know if there are any studies other than those that have already been mentioned. Now, let's talk about something more interesting: You don't need to base your behavior on any study, even if it is scientific. Let's pretend, for example, that we could find a scientifically valid study that shows that people spend 25% more when using a credit card than they do when spending cash.  This does not mean that if you use a credit card, you will spend 25% more.  All it means is that the average person spending with a credit card spends more than the average person paying cash.  But there are outliers.  There are plenty of people who are being frugal while using a credit card, and there are others who spend too much cash.  Everyone's situation is different.  The idea that you will automatically spend less by using cash would not be proven by such a study. When hearing any type of advice like this, you need to look at your own situation and see if it applies to your own life.  And that is what people are doing with the anecdotal comments.  Some say, ""Yep, I spend too much if I use a card."" Others say, ""Actually, I find that when I have cash in my wallet, I spend it on junk.""  And both are correct.  It doesn't matter what the study says the average person does, because you are not average. Now, let's say that you are a financial counselor who helps people work through disastrous financial messes.  Your client has $20,000 in credit card debt and is having trouble paying all his bills.  He doesn't have a budget and never uses cash.  Probably the best advice for this guy is to stop using his card and start paying cash.  It doesn't take a scientific study to see that this guy needs to change his behavior. For what it is worth, I keep a strict budget, keeping track of my spending on the computer.  The vast majority of my spending is electronic.  I find tracking my cash spending difficult, and sometimes I find that when I have cash in my wallet, it seems to disappear without a trace.  :)" "The preferred accounts are designed to hope you do one of several things: Pay one day late.  Then charge you all the deferred interest. Many people think If they put $X a month aside, then pay just before the 6 months, 12 moths or no-payment before 2014 period ends then I will be able to afford the computer, carpet, or furniture. The interest rate they will charge you if you are late will be buried in the fine print. But expect it to be very high. Pay on time, but now that you have a card with their logo on it.  So now you feel that you should buy the accessories from them. They hope that you become a long time customer. They want to make money on your next computer also. Their ""Bill Me Later"" option on that site as essentially the same as the preferred account. In the end you will have another line of credit. They will do a credit check. The impact, both positive and negative, on your credit picture is discussed in other questions.  Because two of the three options you mentioned in your question (cash, debit card) imply that you have enough cash to buy the computer today, there is no reason to get another credit card to finance the purchase. The delayed payment with the preferred account, will save you about 10 dollars (2000 * 1% interest * 0.5 years).  The choice of store might save you more money, though with Apple there are fewer places to get legitimate discounts. Here are your options: How to get the limit increased: You can ask for a temporary increase in the credit limit, or you can ask for a permanent one. Some credit cards can do this online, others require you to talk to them. If they are going to agree to this, it can be done in a few minutes. Some individuals on this site have even been able to send the check to the credit card company before completing the purchase, thus ""increasing"" their credit limit. YMMV. I have no idea if it works.  A good reason to use the existing credit card, instead of the debit card is if the credit card is a rewards card. The extra money or points can be very nice. Just make sure you pay it back before the bill is due. In fact you can send the money to the credit card company the same day the computer arrives in the mail.  Having the transaction on the credit card can also get you purchase protection, and some cards automatically extend the warranty." "No one is quite sure what happened (yet).  Speculation includes: The interesting thing is that Procter & Gamble stock got hammered, as did Accenture.  Both of which are fairly stable companies, that didn't make any major announcements, and aren't really connected to the current financial instability in Greece.  So, there is no reason for there stock prices to have gone crazy like that.  This points to some kind of screw up, and not a regular market force. Apparently, the trades involved in this event are going to be canceled. Edit #1: One thing that can contribute to an event like this is automatic selling triggered by stop loss orders.  Say someone at Citi makes a mistake and sells too much of a stock.  That drives the stock price below a certain threshold.  Computers that were pre-programmed to sell at that point start doing their job.  Now the price goes even lower.  More stop-loss orders get triggered.  Things start to snowball.  Since it's all done by computer these days something like this can happen in seconds.  All the humans are left scratching their heads. (No idea if that's what actually happened.) Edit #2: IEEE Spectrum has a pretty concise article on the topic.  It also includes some links to follow. Edit #3 (05/14/2010): Reuters is now reporting that a trader at Waddell & Reed triggered all of this, but not through any wrongdoing. Edit #4 (05/18/2010): Waddell & Reed claims they didn't do it.  The House Financial Services Subcommittee investigated, but they couldn't find a ""smoking gun"".  I think at this point, people have pretty much given up trying to figure out what happened. Edit #5 (07/14/2010): The SEC still has no idea.  I'm giving up. :-)" Now, if I'm not mistaken, tracking a value-weighted index is extremely easy - just buy the shares in the exact amount they are in the index and wait. Yes in theory. In practise this is difficult. Most funds that track S&P do it on sample basis. This is to maintain the fund size. Although I don't have / know the exact number ... if one wants to replicate the 500 stocks in the same %, one would need close to billion in fund size. As funds are not this large, there are various strategies adopted, including sampling of companies [i.e. don't buy all]; select a set of companies that mimic the S&P behaviour, etc. All these strategies result in tracking errors. There are algorithms to reduce this. The only time you would need to rebalance your holdings is when there is a change in the index, i.e. a company is dropped and a new one is added, right? So essentially rebalance is done to; If so, why do passive ETFs require frequent rebalancing and generally lose to their benchmark index? lets take an Index with just 3 companies, with below price. The total Market cap is 1000  The Minimum required to mimic this index is 200 or Multiples of 200. If so you are fine.    More Often, funds can't be this large. For example approx 100 funds track the S&P Index. Together they hold around 8-10% of Market Cap. Few large funds like Vangaurd, etc may hold around 2%. But most of the 100+ S&P funds hold something in 0.1 to 0.5 range. So lets say a fund only has 100. To maintain same proportion it has to buy shares in fraction. But it can only buy shares in whole numbers. This would then force the fund manager to allocate out of proportion, some may remain cash, etc. As you can see below illustrative, there is a tracking error. The fund is not truly able to mimic the index.  Now lets say after 1st April, the share price moved, now this would mean more tracking error if no action is taken [block 2] ... and less tracking error if one share of company B is sold and one share of company C is purchased.  Again the above is a very simplified view. Tracking error computation is involved mathematics.  Now that we have the basic concepts, more often funds tracking S&P; Thus they need to rebalance. No one at my firm uses python, but we have both long-term algo-managed portfolios as well as very successful day trading strategies. I've worked a bit with both, so if you have any questions I'd be happy to try and answer them and if I can't I'll ask at work next week. "Disclosure: I don't have an iPhone, so I don't use RobinHood.  That being said, I have a less ""they're-out-to-get-ya"" view of what they're doing. As a small business owner (2 businesses), employees cost the most.  If you can create a solid business with few (or no) employees and let robots run it, you will drastically reduce your costs.  Joe Polish said it similarly with sales letters, something along the lines of they never complain about a headache, need to take a year off to discover themself, or just need a personal day.  Robots are the same; they do not have human limits.  Most simple trading can be done and maintained by well written code and AI, there's very little need for humans to do anything other than build it.  Think about the efficiency of bitcoin versus all the central banks combined; how many people are employed by central banks? Robinhood states that they are using technology in these ways to minimize costs and they're using a system that doesn't need physical branches (this doesn't mean they will never have them, just that they don't need them).  Robinhood does not indicate that they allow everything to happen for free; only stock trading.  I worked for a large trading firm once and observed that stock trading wasn't the bulk of where they made their money anyway; trading options, futures, index funds, etc are where the big money was and Robinhood says nothing about those being free.  Like the CQM mentioned too, they'll be charging for margin as well. In a way, the individual stock trader is dead; many people - including this forum - prefer index funds, so more than likely, Robinhood will strike up a deal with an index fund company or create their own (this is just easy, passive income with an expense ratio).  In this category, the markets are their playground, but they do need to attract enough people to their platform, thus free stock trading is a good way to do it. As for selling your information for advertising, that is always a possibility, but they have quite a few other options that would be good for most investors (index funds, affiliating with financial fund companies, etc) where they can start before ever needing to dip their toe in selling information.  This isn't to say they won't do it, but that there are few other options they have. The major concern I have for Robinhood is ongoing security.  Just building it and letting it run kind of assumes that there won't be major compromises in the future and as AI evolves, superior AI might be able to crush older AI." nice work! really enjoyed looking through your website. do you see any possible application of Machine Learning (specifically tensorflow) to this? I was thinking about building a trading bot that uses data from various APIs as a strategy just as an experiment but I'm wondering what your insights are. Most businesses have some sort of software to manage their client data.  Most of these various software and/or services are industry specific.  Black Diamond seems to be a client management tool targeting investment advisers. From the black diamond site Reach an unparalleled level of productivity and transform your client conversations. You don't need one of these unless you're a professional investment adviser with so many clients you can't track them yourself or need more robust reporting or statement generation tools. For your purposes most regular brokers, Fidelity, Schwab, Vanguard, TD, etc, have more than enough tools for the retail level investor.  They have news feeds, security analysis papers, historical data, stock screeners, etc.  You, a regular retail investor doesn't need to buy special software, your broker will generally provide these things as part of the service.