Not really, at least not for all of them. US college endowments, for example, invest into all sorts of things, from highly illiquid developing market investment

Not really, at least not for all of them. US college endowments, for example, invest into all sorts of things, from highly illiquid developing market investments to options, ventures and hedge funds. A couple of times at MIT I saw an overview with a general allocation. I do not remember the details and was not particularly curious, but it certainly had "we can invest in whatever we need and want" flair. It got a >14% average annual investment return for the last 10 years, not something one could get with government bonds. You can look at the endowment reports of the Ivies; many publish some outlines every year.