Do money markets fluctuate during market crashes?
As the commenters have already indicated, money market mutual funds are not guaranteed to maintain principal during all market conditions, and investments in mutual funds are not insured against loss due to market changes. That said, you can run a price search on Vanguard's website and see these results: So, despite all the economic problems since 1975, VMMXX has never traded at a price other than $1.00. "Wikipedia has a solid article on Money Market Funds which includes a section on ""Breaking the Buck"" when the money market fund fails to return its full dollar.  Money market funds smoothing out the daily (generally small) fluctuations of investing in short-term treasuries directly but have similar risk over longer periods.  Some funds can and have lost money in market crashes, though even the worst performers still returned 95+ cents on the dollar. While few investments are guaranteed and likely none in your retirement account,  money-market funds are likely the choice you have with the least fluctuation and similar minimal risk to short term treasuries. However, a second important risk to consider is inflation.  Money market funds generally have returns similar or less than the inflation rate.  While money markets funds help you avoid the fluctuations of the stock market the value of your retirement account falls behind the cost of goods over time.  Unless the investor is fairly old most financial professionals would recommend only a small portion of a retirement account be in money market instruments.  Vanguard also has a set of target retirement investment funds that are close to what many professionals would recommend.  Consulting a financial professional to discuss your particular needs is a good option as well."
"Possible but very unlikely. Money market funds invest in high grade liquid assets and the primary goal is not to lose money. I have not been able to find an example of a Vanguard money market fund ever ""breaking the buck"" and having the value of a share go below a dollar. It is possible that this could happen in the event of a large scale financial collapse, but even then I would call it possible rather than likely." "First, it's an exaggeration to say ""every"" dollar. Traditional mutual funds, including money-market funds, keep a small fraction of their assets in cash for day-to-day transactions, maybe 1%. If you invest $1, they put that in the cash bucket and issue you a share. If you and 999 other people invest $100 each,  not offset by people redeeming, they take the aggregated $100,000 and buy a bond or two. Conversely, if you redeem one share it comes out of cash, but if lots of people redeem  they sell some bond(s) to cover those redemptions -- which works as long as the bond(s) can in fact be sold for close enough to their recorded value. And this doesn't mean they ""can't fail"". Even though they are (almost totally) invested in securities  that are thought to be among the safest and most liquid available,  in sufficiently extreme circumstances those investments can fall in market value,  or they can become illiquid and unavailable to cover ""withdrawals"" (redemptions). ETFs are also fully invested, but the process is less direct. You don't just send money to the fund company. Instead: Thus as long as the underlyings for your ETF hold their value, which for a money market they are designed to, and the markets are open and the market maker firms are operating, your ETF shares are well backed. See https://en.wikipedia.org/wiki/Exchange-traded_fund for more." A market crash won't affect your cash held with your broker - however if the broker defaults (goes bankrupt), you may lose some or all of that cash. If you read the customer agreement that you signed when opening the account, it's very likely that there's a clause that stipulates that under certain circumstances, the broker has the right to use your cash and/or your positions without notice. If the broker default you may not be able to recover the assets they've been using. As an example, look at clause 14 of the Interactive Brokers US customer agreement. This is a fairly standard clause. Depending on your jurisdiction, you may have a partial or full legal protection against such an event (e.g. the SIPC protection for US-based brokers which would apply to you if your broker is IB LLC, even if you are not a US resident/citizen). As JoeTaxpayer has commented, the markets are littered with the carcasses of those who buy into the idea that markets submit readily to formal analysis.   Financial markets are amongst the most complex systems we know of.  To borrow a concept from mathematics - that of a chaotic system - one might say that financial markets are a chaotic system comprised of a nested structure of chaotic subsystems. For example, the unpredictable behaviour of a single (big) market participant can have dramatic effects on overall market behaviour. In my experience, becoming a successful investor requires a considerable amount of time and commitment and has a steep learning curve.  Your actions in abandoning your graduate studies hint that you are perhaps lacking in commitment. Most people believe that they are special and that investing will be easy money.  If you are currently entertaining such thoughts, then you would be well advised to forget them immediately and prepare to show some humility. TL/DR; It is currently considered that behavioural psychology is a valuable tool in understanding investors behaviour as well as overall market trends.  Also in the area of psychology, confirmation bias is another aspect of trading that it is important to keep in mind.  Quantitative analysis is a mathematical tool that is currently used by hedge funds and the big investment banks, however these methods require considerable resources and given the  performance of hedge funds in the last few years, it does not appear to be worth the investment. If you are serious in wanting to make the necessary commitments, then here are a few ideas on where to start : There are certain technical details that you will need to understand in order to quantify the risks you are taking beyond simple buying and holding financial instruments.  For example, how option strategies can be used limit your risk; how margin requirements may force your hand in volatile markets; how different markets impact on one another - e.g., the relationship between bond markets and equity markets; and a host of other issues.  Also, to repeat, it is important to understand how your own psychology can impact on your investment decisions. Yes, this phenomenon is well documented.  A collapse of an economy's exchange rate is coincidented with a collapse in its equities market.    The recent calamities in Turkey, etc during 2014 had similar results. Inflation is highly correlated to valuations, and a collapse of an exchange rate is highly inflationary, so a collapse of an exchange rate is highly correlated to a collapse in valuations. Your asset mix should reflect your own risk tolerance.  Whatever the ideal answer to your question, it requires you to have good timing, not once, but twice. Let me offer a personal example. In 2007, the S&P hit its short term peak at 1550 or so. As it tanked in the crisis, a coworker shared with me that he went to cash, on the way down, selling out at about 1100. At the bottom, 670 or so, I congratulated his brilliance (sarcasm here) and as it passed 1300 just 2 years later, again mentions how he must be thrilled he doubled his money. He admitted he was still in cash. Done with stocks. So he was worse off than had he held on to his pre-crash assets. For sake of disclosure, my own mix at the time was 100% stock. That's not a recommendation, just a reflection of how my wife and I were invested.  We retired early, and after the 2013 excellent year, moved to a mix closer to 75/25. At any time, a crisis hits, and we have 5-6 years spending money to let the market recover. If a Japanesque long term decline occurs, Social Security kicks in for us in 8 years.  If my intent wasn't 100% clear, I'm suggesting your long term investing should always reflect your own risk tolerance, not some short term gut feel that disaster is around the corner. "https://en.wikipedia.org/wiki/Irrational_exuberance  &gt; Clearly, sustained low inflation implies less uncertainty about the future, and lower risk premiums imply higher prices of stocks and other earning assets. We can see that in the inverse relationship exhibited by price/earnings ratios and the rate of inflation in the past. But how do we know when irrational exuberance has unduly escalated asset values, which then become subject to unexpected and prolonged contractions as they have in Japan over the past decade?  &gt; — ""The Challenge of Central Banking in a Democratic Society"", 1996-12-05" (After seeing your most recent comment on the original question, it looks like others have answered the question you intended, and described the extreme difficulty of getting the timing right the way you're trying to. Since I've already typed it up, what follows answers what I originally thought your question was, which was asking if there were drawbacks to investing entirely in money market funds to avoid stock volatility altogether.) Money market funds have the significant drawback that they offer low returns. One of the fundamental principles in finance is that there is a trade-off between low risk and high returns. While money market funds are extremely stable, their returns are paltry; under current market conditions, you can consider them roughly equivalent to cash. On the other hand, though investing in stocks puts your money on a roller coaster, returns will be, on average, substantially higher. Since people often invest in order to achieve personal financial stability, many feel naturally attracted to very stable investments like money market funds. However, this tendency can be a big mistake. The higher returns of the stock market don't merely serve to stoke an investor's greed, they are necessary for achieving most people's financial goals. For example, consider two hypothetical investors, saving for retirement over the course of a 40-year career. The first investor, apprehensive Adam, invests $10k per year in a money market fund. The second investor, brave Barbara, invests $10k per year in an S&P 500 index fund (reinvesting dividends). Let's be generous and say that Adam's money market fund keeps pace with inflation (in reality, they typically don't even do that). At the end of 40 years, in today's money, Adam will have $10,000*40 = $400,000, not nearly enough to retire comfortably on. On the other hand, let's assume that Barbara gets returns of 7% per year after inflation, which is typical (though not guaranteed). Barbara will then have, using the formula for the future value of an annuity, $10,000 * [(1.07)^40 - 1] / 0.07, or about $2,000,000, which is much more comfortable. While Adam's strategy produces nearly guaranteed results, those results are actually guaranteed failure. Barbara's strategy is not a guarantee, but it has a good chance of producing a comfortable retirement. Even if her timing isn't great, over these time scales, the chances that she will have more money than Adam in the end are very high. (I won't produce a technical analysis of this claim, as it's a bit complicated. Do more research if you're interested.) The dynamics of different contracts and liquidity can be quite different on the last day on the month and for intraday trade make sure you use bid-ask data as opposed to historical trades.  I'm not saying whether it works or not, but im just giving you ideas to improve your testing. There's an interview with Andrew Lo on the WSJ that's worth a listen. One idea he touched on briefly is how the rise of index funds may be creating an investor monoculture. If this is the case, then he thinks it could lead to more market volatility. Interesting stuff.  http://www.wsj.com/podcasts/andrew-w-lo-talks-how-to-evolve-with-adaptive-markets/4B141ED2-23EA-409E-BFEE-96791EEB473E.html Low volatility trading tends to be a hallmark of the late summer as Wall Street by and large goes on summer vacation. When all those traders and hedge fund managers return to work full-tilt in September,  the market tends to become more volatile - either upwards or downwards. If you are wondering why these months have been particularly poor relative to others, than I don't think anyone knows the reason why. A market correction has been expected for several weeks. It happens all the time, but people need an excuse to panic. Sometimes, I think panic is their usual state and they just look for fuel to keep it going because they can't handle boredom. "From my limited experience with foreign exchange... Money is a commodity.. people buy it and sell it like other products.. if ""money"" is in demand the price goes up.. this is the case when a countries stocks are hot, and you need to purchase that countries currency to buy that stock... I've also seen the currency rise on news and speculation.  Many years ago, I administered foreign receivables... My job was to settle letters of credit from Britain... I remember on one ocassion Margaret Thatcher said something to upset the markets.. her remark caused the price of the UK pound to fluctuate." By all measures, the U.S. stock market is currently frothy. The apparent stability of the world financial system is superficial – financial asset prices are not real, the equilibrium is temporary, the lack of volatility is a trap, and when the whole thing goes haywire, there will truly be hell to pay. Volatility typically decreases when stocks rise except pending news events or fast markets.  It has a great impact of the premium of the option.