It's weird how most of the return from bonds comes not from yield but from capital appreciation [1], which happens because yields are dropping. There's something perverse and circular about it: "Make sure you buy your collectible widget today! It'll go up in value, because next year's widgets won't be as good! Prices only go up, because everything's downhill from here!"
About [1]: I'm wrong. If you look at TLT in TradingView, adjusted for "dividends" vs. not, from 2003 to 2019 you see nominal gains of about 150% (with) vs. 40% (without). So most gain is from income. That's ignoring tax.
Would also be good to compare to CPI to understand real returns. Or whatever other number seems to be a truer measure of inflation (house prices, for example).
[1] Actually, is this literally true?