If we could see disasters coming, they wouldn’t become disasters. Oil’s price is down 71% since June of 2014, and while some factors that triggered the tumble seemed obvious at the time, others hit our blind side. Most investors assumed that China’s slowdown would hurt oil. But most also believed that Saudi Arabia and U.S. producers would put a floor under prices by cutting production; that didn’t happen, in part because the Americans needed to keep cash flowing to service hefty debts.

Shawn Driscoll, natural-resources portfolio manager at T. Rowe Price, told Fortune in November that oil could go to $30 this year. He says the low 20s now look realistic, and adds, “I don’t think 2016 will be the ultimate low” for oil.

For more on crude oil’s price, watch this Fortune video:

A version of this article appears in the February 1, 2016 issue of Fortune with the headline “Tracking Oil’s Collapse.”