It's usually assumed (and many people actually prove it with assorted mathematical gesticulations) that bond prices move in a direction opposite to interest rates.

>Huh?
When interest rates fall, you expect bond prices to rise. When interest rates rise ...
>Bond prices fall, eh?
Yes. That's what you'd expect.
>And you avoid trying to prove this, right ?
Uh .. not exactly. I did some stuff on bonds here.
However, my motto has always been ...
>Don't tell me! One should use actual data and not mathematical proxies!

Well, yes ... so here's a few Vanguard mutual funds and how they relate to interest rates:

and the first part, amplified:

>And your conclusion?
I conclude that ...
>Don't tell me! One should use actual data and not mathematical proxies!
You got it