The Asset Allocation Paradox
Asset Allocation serves many purposes, not just mitigating risk via a diversification of asset classes, but also allowing you to take a level of risk that is appropriate for a given investor at a given time by how much is allocated to which asset classes. A younger investor with a longer timeframe, may wish to take a lot more risk, investing heavily in equities, and perhaps managed funds that are of the 'aggressive growth' variety, seeking better than market returns. Someone a little older may wish to pull back a bit, especially after a bull market has brought them substantial gains, and begin to 'take money off the table' perhaps by starting to establish some fixed income positions, or pulling back to slightly less risky index,  'value' or 'balanced' funds. An investor who is near or in retirement will generally want even less risk, going to a much more balanced approach with half or more of their investments in fixed income, and the remainder often in income producing 'blue chip' type stocks, or 'income funds'.  This allows them to protect a good amount of their wealth from potential loss at a time when they have to be able to depend on it for a majority of their income. An institution such as Yale has very different concerns, and may always be in a more aggressive 'long term' mode since 'retirement' is not a factor for them.  They are willing to invest mostly in very aggressive ways, using diversification to protect them from one of those choices 'tanking' but still overall taking a pretty high level of risk, much more so than might be appropriate for an individual who will generally need to seek safety and to preserve gains as they get older.  For example look at the PDF that @JLDugger linked, and observe the overall risk level that Yale is taking, and in addition observe the large allocations they make to things like private equity with a 27%+ risk level compared to their very small amount of fixed income with a 10% risk level.  Yale has a very long time horizon and invests in a way that is atypical of the needs and concerns of an individual investor.  They also have as you pointed out, the economy of scale (with something like #17B in assets?) to afford to hire proven experts, and their own internal PHD level experts to watch over the whole thing, all of which very few individual investors have. For either class of investor, diversification, is a means to mitigate risk by not having all your eggs in one basket.  Via having multiple different investments (such as picking multiple individual stocks, or aggressive funds with different approaches, or just an index fund to get multiple stocks) you are protected from being wiped out as might happen if a single choice might fail.  For example imagine what would have happened if you had in 2005 put all your money into a single stock with a company that had been showing record profits  such as Lehman Brothers, and left it there until 2008 when the stock tanked. or even faster collapses such as Enron, etc that all 'looked great' up until shortly after they failed utterly.   Being allocated across multiple asset classes provides some diversification all on it's own, but you can also be diversified within a class. Yale uses the diversification across several asset classes to have lower risk than being invested in a single asset class such as private equity. But their allocation places much more of their funds in high risk classes and much less of their funds in the lowest risk classes such as fixed income. "I recommend you take a look at this lecture (really, the whole series is enlightening), from Swenson. He identifies 3 sources of returns: diversification, timing and selection. He appears to discard timing and selection as impossible. A student kinda calls him out on this. Diversification reduces risk, not increase returns. It turns out they did time the market, by shorting .com's before the bubble, and real estate just before the downturn. In 1990, Yale started a ""Absolute Return"" unit and allocated like 15 percent to it, mostly by selling US equities, that specializes in these sorts of hedging moves. As for why you might employ managers for specific areas, consider that the expense ratio Wall Street charges you or me still represent a very nice salary when applied to the billions in Yale's portfolio. So they hire internally to reduce expenses, and I'm sure they're kept busy. They also need people to sell off assets to maintain ratios, and figuring out which ones to sell might take specialized knowledge. Finally, in some areas, you functionally cannot invest without management. For example, Yale has a substantial allocation in private equity, and by definition that doesn't trade on the open market. The other thing you should consider is that for all its diversification, Yale lost 25 percent of their portfolio in 2009. For a technique that's supposed to reduce volatility, they seem to have a large range of returns over the past five years."
Since you already have twice your target in that emergency fund, putting that overage to work is a good idea. The impression that I get is that you'd still like to stay on the safe side. What you're looking for is a Balanced Fund.  In a balanced fund the managers invest in both stocks and bonds (and cash). Since you have that diversification between those two asset classes, their returns tend to be much less volatile than other funds. Also, because of their intended audience and the traditions from that class of funds' long history, they tend to invest somewhat more conservatively in both asset classes.  There are two general types of balanced funds: Conservative Allocation funds and Moderate Allocation funds. Conservative allocation funds invest in more fixed income than equity (the classic mix is 60% bonds, 40% stocks). Moderate allocation funds invest in more equity than fixed income (classic mix: 40% bonds, 60% stocks). A good pair of funds that are similar but exemplify the difference between conservative allocation and moderate allocation are Vanguard's Wellesley Income Fund (VWINX) for the former and Vanguard's Wellington Fund (VWELX) for the latter. (Disclaimer: though both funds are broadly considered excellent, this is not a recommendation.) Good luck sorting this out! If you have retirement savings, the HSA should not be considered in isolation, but as part of your complete asset allocation.  The HSA is a unique account in that the funds go in pre-tax, grow tax free, and then for qualified expenses, are withdrawn tax free. With healthcare being the biggest risk to one's retirement portfolio (i.e. a large unknown in that retirement budget), funding an HSA to the max, and treating it as a long term investment makes a lot of sense.  As a comment suggests, keeping what you feel is a year's worth of expenses liquid might make sense. The (medical) plan coverage should have a maximum out of pocket each year. That's another number you can use as a guideline.  The question is great, and as more people have the high deductible plan with an HSA, it's worth some analysis. The problem for those answering is that we don't know the rest of your situation. Specifically, how these funds fit into your portfolio of assets. The Investopedia article you linked to is a good start. Its key takeaway is that you should always consider risk-adjusted return when evaluating your portfolio. In general, investors seeking a higher level of return must face a higher likelihood of taking a loss (risk). Different types of stocks (large vs small; international vs US; different industry sectors) have different levels of historical risk and return. Not to mention stocks vs bonds or other financial instruments... So, it's key to make an apples-to-apples comparison against an appropriate benchmark. A benchmark will tell you how your portfolio is doing versus a comparable portfolio. An index, such as the S&P 500, is often used, because it tells you how your portfolio is doing compared against simply passively investing in a diversified basket of securities. First, I would start with analyzing your portfolio to understand its asset allocation. You can use a tool like the Morningstar X-Ray to do this. You may be happy with the asset allocation, or this tool may inform you to adjust your portfolio to meet your long-term goals. The next step will be to choose a benchmark. Given that you are investing primarily in non-US securities, you may want to pick a globally diversified index such as the Dow Jones Global Index. Depending on the region and stock characteristics you are investing in, you may want to pick a more specialized index, such as the ones listed here in this WSJ list. With your benchmark set, you can then see how your portfolio's returns compare to the index over time. IRR and ROI are helpful metrics in general, especially for corporate finance, but the comparison-based approach gives you a better picture of your portfolio's performance. You can still calculate your personal IRR, and make sure to include factors such as tax treatment and investment expenses that may not be fully reflected by just looking at benchmarks. Also, you can calculate the metrics listed in the Investopedia article, such as the Sharpe ratio, to give you another view on the risk-adjusted return. If an advisor uses asset allocation and risk management in conjunction with financial planning, performance will be adequate for each client's goals in the LONG RUN. Past performance doesn't mean shit for the future and imo, bragging on performance in a prospect meeting signals that they don't have any other value to lean on and likely take on more risk than they should to show that performance. This is hyperbole that makes assumptions about engineering details that are easily addressed: Use a system analogous to marginal tax rates to solve this problem.  Have 0-tax cutoff values a few times larger than expected pension/retirement fund savings values for individuals. Here's the original academic backbone that it's based on and expanded upon.  https://en.m.wikipedia.org/wiki/Modigliani%E2%80%93Miller_theorem  I think thats it's overly conservative in this case (I fully accept academic theories only go so far in the real world) as Damodaran (NYU professor) has made a pretty solid case that cash on balance sheet at large cap tech companies is valued by the markets at less than its after tax $ value. Most of the “recommendations” are just total market allocations.  Within domestic stocks, the performance rotates. Sometimes large cap outperform, sometimes small cap outperform. You can see the chart here (examine year by year):  https://www.google.com/finance?chdnp=1&chdd=1&chds=1&chdv=1&chvs=maximized&chdeh=0&chfdeh=0&chdet=1428692400000&chddm=99646&chls=IntervalBasedLine&cmpto=NYSEARCA:VO;NYSEARCA:VB&cmptdms=0;0&q=NYSEARCA:VV&ntsp=0&ei=_sIqVbHYB4HDrgGA-oGoDA Conventional wisdom is to buy the entire market. If large cap currently make up 80% of the market, you would allocate 80% of domestic stocks to large cap.  Same case with International Stocks (Developed). If Japan and UK make up the largest market internationally, then so be it.  Similar case with domestic bonds, it is usually total bond market allocation in the beginning.  Then there is the question of when you want to withdraw the money. If you are withdrawing in a couple years, you do not want to expose too much to currency risks, thus you would allocate less to international markets. If you are investing for retirement, you will get the total world market.  Then there is the question of risk tolerance. Bonds are somewhat negatively correlated with Stocks. When stock dips by 5% in a month, bonds might go up by 2%. Under normal circumstances they both go upward. Bond/Stock allocation ratio is by age I’m sure you knew that already.  Then there is the case of Modern portfolio theory. There will be slight adjustments to the ETF weights if it is found that adjusting them would give a smaller portfolio variance, while sacrificing small gains. You can try it yourself using Excel solver.  There is a strategy called Sector Rotation. Google it and you will find examples of overweighting the winners periodically. It is difficult to time the rotation, but Healthcare has somehow consistently outperformed. Nonetheless, those “recommendations” you mentioned are likely to be market allocations again.  The “Robo-advisors” list out every asset allocation in detail to make you feel overwhelmed and resort to using their service. In extreme cases, they can even break down the holdings to 2/3/4 digit Standard Industrial Classification codes, or break down the bond duration etc.  Some “Robo-advisors” would suggest you as many ETF as possible to increase trade commissions (if it isn’t commission free). For example, suggesting you to buy VB, VO, VV instead a VTI. When we 'delta-hedge', we make the value of a portfolio 0.  No - you make the risk relative to some underlying 0.  The portfolio does have a value, but if whatever underlying you're hedging against changes slightly the value of your portfolio should not change. But, what is the derivative of a portfolio?  It's the instantaneous rate of change of the portfolio) relative to some underlying phenomenon.  With a portfolio of many stocks, there's not one single factor that drives the value of your portfolio. You have sensitivity to each underlying stock (price and volatility), interest rates, the market as a whole, etc. For simplicity, we might imagine a portfolio that has holdings in .... a call .... a stock .... and a bank account (to borrow and lend money).  You will have a delta relative to the stock and a delta relative to the underlying instrument on the option, etc.  Those can only be aggregated for each factor (e.g. if the call is an option on the same stock) Theta is the only one you can calculate for the portfolio as a whole - it will be the aggregate theta of all of your positions (since change in time is constant across all investments).  All of the others are not aggregatable since they are measuring sensitivities to different phenomena.