I agree. The difference is that at large levels of wealth, levels beyond what most of us can realistically imagine happening, then storage becomes an issue. N

I agree. The difference is that at large levels of wealth, levels beyond what most of us can realistically imagine happening, then storage becomes an issue. No regular person is going to buy a bond with a negative interest rate. Just hold cash. But once you start to have large amounts of cash, different considerations enter the picture. How do you store it? Security guards. Guards to watch the security guards. Too much cash is hard to spend, so you want it in electronic form. The market is now saying that for certain types of cash in electronic form, the risk adjusted fee for creating the electronic record and holding it for you is greater than the interest they will pay you for the money. In that way, the net interest rate including all factors such as the risk of default, ends up negative.