Lump Sum Investing vs. Dollar Cost Averaging (as a Long Term Investor)
I think you're not applying the right time scale here. ESPP (Employee Stock Purchase Plan) is usually vesting every 6 months. So every half a year you receive a chunk of stocks based on your salary deduction, with the 15% discount. Every half a year you have a chunk of money from the sale of these stocks that you're going to put into your long term investment portfolio. That is dollar cost averaging. You're investing periodically (every 6 months in this case), same (based on your salary deferral) amount of money, regardless of the stock market behavior. That is precisely what dollar cost averaging is.
What are the risks pertaining to timing on long term index   investments? The risks are countless for any investment strategy.  If you invest in US stocks, and prices revert to the long term cyclically adjusted average, you will lose a lot of money.  If you invest in cash, inflation may outpace interest rates and you will lose money.  If you invest in gold, the price might go down and you will lose money.  It's best to study history and make a reasonable decision (i.e. invest in stocks). Here are long term returns by asset class, computed by Jeremy Siegel:  $1 invested in equities in 1801 equals $15.22 today if was not invested and $8.8 million if it was invested in stocks.  This is the 'magic of compound interest' and cash / bonds have not been nearly as magical as stocks historically. 2) How large are these risks? The following chart shows the largest drawdowns (decreases in the value of an asset) since 1970 (source):  Asset prices decrease in value frequently.  Financial assets are volatile, but historically, they have increased over time, enabling investors to earn compounded returns (exponential growth of money is how to get rich).  I personally view drawdowns as an excellent time to buy - it's like going on a shopping spree when everything in the store is discounted. 3) In case I feel not prepared to take these risks, how can I avoid   them? The optimal asset allocation depends on the ability to take risk and your tolerance for risk.  You are young and have a long investment horizon, so if stocks go down, you will have plenty of time to wait for them to go back up (if you're smart, you'll buy more stocks when they go down because they're cheap), so your ability to bear risk is high.  From your description, it seems like you have a low risk tolerance (despite a high ability to be exposed to risk).  Here's the return of various asset classes and how the average investor has fared over the last 20 years (source):  Get educated (read Common Sense on Mutual Funds, A Random Walk Down Wall Street, etc.) and don't be average! Closing words: Investing in a globally diversified portfolio with a dollar cost averaging strategy is the best strategy for most investors.  For investors that are unable to stay rational when markets are volatile (i.e. the investor uncontrollably sells their stocks when stocks decrease 20%), a more conservative asset allocation is recommended.  Due to the nature of compounded interest, a conservative portfolio is likely to have a much lower future value. There is a difference between trading which is short term focussed and investing which is longterm focussed. On the long term what drives stock prices is still the overall economy and the performance of the underlying business aspects. I do not think that any trading algorithms will change this. These are more concerned with short term profits regardless of the underlying business economics. Therefore I think that longterm investing using index funds is still a viable strategy for most private investors. Common financial advice is just that - it is common and general in nature and not specific for your financial needs, your goals and your risk tolerance. Regarding the possibility of a US market not going anywhere over a long period of time, well it is not a possibility, it has happened. See chart below:  It took 13 years for the S&P 500 to break through 1550, a level first reached in March 2000, tested in October 2007 (just before the GFC) and finally broken through in March 2013. If you had bought in early 2000 you would still be behind when you take inflation into account. If you took the strategy of dollar cost averaging and bought the same dollar value (say $10,000) of the index every six months (beginning of each January and each July) starting from the start of 2000 and bought your last portion in January 2013, you would have a return of about 35% over 13.5 years (or an average of 2.6% per year). Now lets look at the same chart below, but this time add some trend lines.  If we instead bought whenever the price crossed above the downtrend-line and sold whenever the price crossed below the uptrend-line (with the first purchase at the start of January 2000), we would have a return of 93% over the 13.5 years (or an average of 6.9% per year). Another more aggressive option (but manageable if you incorporate a risk management strategy) is to buy long when the price crosses the downtrend-line and sell your existing long position and sell short when the price drops below the uptrend-line. That is profiting both up-trending and down-trending markets. Again we start our buying at the start of January 2000. By shorting the index when the market is in a down-trend you could increase the above returns of 93% by another 54%, for a total return of 147% over 13.5 years (or an average of 10.9% per year). To conclude, using a simple long term strategy to time the markets may result in considerably higher returns than dollar cost averaging over the medium to long term, and I know which strategy would help me sleep better at night. I believe that the Wikipedia article is attempting to draw a difference between dollar cost averaging as a result of investing when money becomes available (i.e. 401k contributions from your paycheck) and spreading out a lump sum investment. For the former you want to continuously invest as the money becomes available following your predetermined plan for allocation. For the later it may be reasonable to consider the market as you decide how and the timing for investing. "Can you easily stomach the risk of higher volatility that could come with smaller stocks? How certain are you that the funds wouldn't have any asset bloat that could cause them to become large-cap funds for holding to their winners? If having your 401(k) balance get chopped in half over a year doesn't give you any pause or hesitation, then you have greater risk tolerance than a lot of people but this is one of those things where living through it could be interesting. While I wouldn't be against the advice, I would consider caution on whether or not the next 40 years will be exactly like the averages of the past or not. In response to the comments: You didn't state the funds so I how I do know you meant index funds specifically? Look at ""Fidelity Low-Priced Stock"" for a fund that has bloated up in a sense. Could this happen with small-cap funds? Possibly but this is something to note. If you are just starting to invest now, it is easy to say, ""I'll stay the course,"" and then when things get choppy you may not be as strong as you thought. This is just a warning as I'm not sure you get my meaning here. Imagine that some women may think when having a child, ""I don't need any drugs,"" and then the pain comes and an epidural is demanded because of the different between the hypothetical and the real version. While you may think, ""I'll just turn the cheek if you punch me,"" if I actually just did it out of the blue, how sure are you of not swearing at me for doing it? Really stop and think about this for a moment rather than give an answer that may or may not what you'd really do when the fecal matter hits the oscillator. Couldn't you just look at what stocks did the best in the last 10 years and just buy those companies? Think carefully about what strategy are you using and why or else you could get tossed around as more than a few things were supposed to be the ""sure thing"" that turned out to be incorrect like the Dream Team of Long-term Capital Management, the banks that were too big to fail, the Japanese taking over in the late 1980s, etc. There are more than a few times where things started looking one way and ended up quite differently though I wonder if you are aware of this performance chasing that some will do." If you're worried about investing all at once, you can deploy your starting chunk of cash gradually by investing a bit of it each month, quarter, etc. (dollar-cost averaging).  The financial merits and demerits of this have been debated, but it is unlikely to lose you a lot of money, and if it has the psychological benefit of inducing you to invest, it can be worth it even if it results in slightly less-than-optimal gains. More generally, you are right with what you say at the end of your question: in the long run, when you start won't matter, as long as you continue to invest regularly.  The Boglehead-style index-fund-based theory is basically that, yes, you might save money by investing at certain times, but in practice it's almost impossible to know when those times are, so the better choice is to just keep investing no matter what.  If you do this, you will eventually invest at high and low points, so the ups and downs will be moderated. Also, note that from this perspective, your example of investing in 2007 is incorrect.  It's true that a person who put money in 2007, and then sat back and did nothing, would have barely broken even by now.  But a person who started to invest in 2007, and continued to invest throughout the economic downturn, would in fact reap substantial rewards due to continued investing throughout the post-2007 lows.  (Happily, I speak from experience on this point!) "Ah I got ya. I partially agree with you, but it's far more complex. I think that is simplifying the debate a bit too much. When people go ""passive"" you are making the assumption that they are able to stay fully invested the full time period (say 30-40 years until retirement when you might change the asset allocation). This is not a fair assumption because many studies on behavioral finance have shown that people (90% plus) are not able to sit tight through a full market cycle and often sell out during a bear market. I'm not debating you're point that passive often outperforms due to the fees (although there are many managers that do outperform), but the main issue with self-managing and passive investing is people usually make emotional decisions, which then hurts their long-term performance. This would be the reason to hire an adviser. Assuming that people are able to stay passive the entire time and not make a single ""active"" decision is a very unfair assumption. There was a good study on this referenced in Forbes article below: https://www.forbes.com/sites/advisor/2014/04/24/why-the-average-investors-investment-return-is-so-low/#5169be2b111a  Another issue is that there are a lot ""active managers"" that really just replicate their benchmarks and don't actually actively manage. If you look at active managers who really do have huge under-weights and over-weights relative to their benchmarks they actually tend to outperform them (look at the study below by martin cremers, he's one of the most highly respected researchers when it comes to investment performance research and the active vs passive debate)  http://www.cfapubs.org/doi/pdf/10.2469/faj.v73.n2.4  I guess what I'm trying to say is that for most people having an adviser (and paying them a 1% fee) is usually better than going it alone, where they are going to A. chase heat (I bet they always choose the hottest benchmark from the past few years) and B. make poor emotional decisions relating their finances." Many would recommend lump sum investing because of the interest gains, and general upward historical trend of the market.  After introducing DCA in A Random Walk Down Wall Street, Malkiel says the following: But remember, because there is a long-term uptrend in common-stock prices, this technique is not necessarily appropriate if you need to invest a lump sum such as a bequest. If possible, keep a small reserve (in a money fund) to take advantage of market declines and buy a few extra shares if the market is down sharply. I’m not suggesting for a minute that you try to forecast the market. However, it’s usually a good time to buy after the market has fallen out of bed. Just as hope and greed can sometimes feed on themselves to produce speculative bubbles, so do pessimism and despair react to produce market panics. - A Random Walk Down Wall Street, Burton G. Malkiel He goes on from there to recommend a rebalancing strategy. Dollar cost averaging is a method of regularly investing money as it is available.  For example, $100 from each paycheck.  It has been shown to bet better, on average, than collecting the money and investing it all at once.  It is not intended to be used when you have the entire amount up front.  See this link. Dollar cost averaging a lump sum would only be beneficial if the market was just as likely to go up as is to go down.  Since, over time, the market (historically) has always gone up, your best bet is to invest all of your money right away.  Anything else is just trying to time the market. If you are going to the frenzy of individual stock picking, like almost everyone initially, I suggest you to write your plan to paper. Like, I want an orthogonal set of assets and limit single investments to 10%. If with such limitations the percentage of brokerage fees rise to unbearable large, you should not invest that way in the first hand.  You may find better to invest in already diversified fund, to skip stupid fees. There are screeners like in morningstar that allow you to see overlapping items in funds but in stocks it becomes trickier and much errorsome. I know you are going to the stock market frenzy, even if you are saying to want to be long-term or contrarian investor, most investors are convex, i.e. they follow their peers, despite it would better to be a concave investor (but as we know it can be hard).  If the last part confused you, fire up a spreadsheet and do a balance. It is a very motivating activity, really. You will immediately notice things important to you, not just to providers such as morningstar, but alert it may take some time. And Bogleheads become to your rescue, ready spreadsheets here. Dollar cost averaging is beneficial if you don't have the money to make large investments but are able to add to your holding over time. If you can buy the same monetary amount at regular intervals over time, your average cost per share will be lower than the stock's average value over that time. This won't necessarily get you the best price, but it will get you, on the whole, a good price and will enable you to increase your holdings over time. If you're doing frequent trading on a highly volatile stock, you don't want to use this method. A better strategy is to buy the dips: Know the range, and place limit orders toward the bottom of the range. Then place limit orders to sell toward the high end of the range. If you do it right, you might be able to build up enough money to buy and sell increasing numbers of shares over time. But like any frequent trader, you'll have to deal with transaction fees; you'll need to be sure the fees don't eat all your profit. Dollar cost averaging doesn't (or shouldn't) apply here. DCA is the natural way we invest in the market, buying in by a steady dollar amount each pay period, so over time we can buy more shares when the market is down, and fewer when it's higher. It's more psychological than financial. The fact is that given the market rises, on average, over time, if one has a lump sum to invest, it should be deployed based on other factors, not just DCA'd in. As I said, DCA is just how we all naturally invest from our income.  The above has nothing to do with your situation. You are invested and wish to swap funds. If the funds are with the same broker, you should be able to execute this at the closing price. The sell and buy happen after hours and you wake up the next day with the newly invested portfolio.  If funds are getting transferred from broker to broker, you do have a risk. The risk that they take time, say even 2 days when funds are not invested. A shame to lose a 2% market move as the cost of moving brokers. In this case, I'd do mine and my wife's at different times. To reduce that risk. "Generally investing in index-tracking funds in the long term poses relatively low risk (compared to ""short term investment"", aka speculation). No-one says differently. However, it is a higher risk than money-market/savings/bonds. The reason for that is that the return is not guaranteed and loss is not limited. Here volatility plays part, as well as general market conditions (although the volatility risk also affects bonds at some level as well). While long term trend may be upwards, short term trend may be significantly different. Take as an example year 2008 for S&P500. If, by any chance, you needed to liquidate your investment in November 2008 after investing in November 1998 - you might have ended up with 0 gain (or even loss). Had you waited just another year (or liquidated a year earlier) - the result would be significantly different. That's the volatility risk. You don't invest indefinitely, even when you invest long term. At some point you'll have to liquidate your investment. Higher volatility means that there's a higher chance of downward spike just at that point of time killing your gains, even if the general trend over the period around that point of time was upward (as it was for S&P500, for example, for the period 1998-2014, with the significant downward spikes in 2003 and 2008). If you invest in major indexes, these kinds of risks are hard to avoid (as they're all tied together). So you need to diversify between different kinds of investments (bonds vs stocks, as the books ""parrot""), and/or different markets (not only US, but also foreign)." If you are making regular periodic investments (e.g. each pay period into a 401(k) plan) or via automatic investment scheme in a non-tax-deferred portfolio (e.g. every month, $200 goes automatically from your checking account to your broker or mutual fund house), then one way of rebalancing (over a period of time) is to direct your investment differently into the various accounts you have, with more going into the pile that needs bringing up, and less into the pile that is too high. That way, you can avoid capital gains or losses etc in doing the selling-off of assets. You do, of course, take longer to achieve the balance that you seek, but you do get some of the benefits of dollar-cost averaging. You need an accountant and/or a lawyer who is familiar with the US tax code and the rules in South Korea (assuming from your tag). As the interest will be money generated in the US, you could be required to withhold some of the interest and remit it to the IRS (I believe 30% withholding rate). Since South Korea is a treaty country, your friend can complete and sign a form W8-BEN and give it to you, so you may withhold a lower amount. Your friend would need to file a return if too much was withheld. They may also get taxed in South Korea. There are probably rules in South Korea about minimum interest that must be charged, similar to Applicable Federal Rates for the US, so check with your accountant or lawyer for this. If you craft it correctly, you will be able to have a loan as a mortgage (with the house properly secured), which then would allow you to deduct mortgage interest rates from your return. As far as I am aware, there is no maximum amount for loans.