Ten months ago, Jeremy Siegel issued a dire warning about the trajectory of prices. "The money supply since the beginning of the pandemic, so a little over a year, has gone up almost 30 percent. Now, that money is not going to disappear. That money is going to find its way into spending and into higher prices," Siegel, a professor of finance at the University of Pennsylvania's Wharton School, told CNBC during an interview on May 14. "Over the next two, three years we could easily have 20 percent inflation with this increase in the money supply."