history, and the causes.
Predictions of when they will pop are usually not accurate, but the cause and the results are.
Look at the video clips of Peter Schiff warning about the bubble economy back in 2005-2007 & how all of the experts were laughing at him and making fun of him & then see how accurate his predictions were:
https://www.youtube.com/watch?v=sgRGBNekFIw
Or read some of the exact details of what he was predicting in the lead up to the monster crash and how spot on they were:
http://seekingalpha.com/article/181774-fed-to-people-it-s-not-our-fault