For a lot of wealthy investors that look to stockpile or inventory their wealth, either as an emergency fund or dry powder, the Vanguard Total Bond Index (VBMFX) is a popular choice because it is loaded with nothing but U.S. government-issued debt as well as some AAA and AA bonds.
It is distinguishable from a money market fund because it owns most of the same debt instruments, except for longer durations. If you purchase those $1 shares in a money market fund, you are making the safest short-term investment possible because it is nothing but U.S. government debt that matures in thirty days or less. As long as the U.S. government does not imminently dissolve its obligations, you are getting paid. That’s why the interest collected is often less than a tenth of one percent.