I love financial and economic time series that have a long history. Good ones that are older than World War II are hard to come by - here is one of them:
Aaa bonds have the best credit rating out there. Baa bonds aren’t in the non-investment grade or high yield classification but they are rated lower than Aaa, so they carry a higher yield. Sometimes the difference between the two bonds diverges a little but the main driver for both is underlying treasury rates.
Bond yields have moved in long-term cycles, with the most recent down cycle starting in the early 1980s. The real question is how much lower can they go?
That’s an answer that’ll be decided by treasury rates. While they say negative yields are unlikely, with everything going on these days, I don’t really like to rule anything out anymore.