Offer your insights or judgment on the input financial query or topic using your financial expertise. Reply as normal question answering

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.