lifestyle leader

In a speech to the Japan Society in New York, Blackstone CEO Stephen Schwarzman said:

"Between 40 and 45 percent of the world's wealth has been destroyed in little less than a year and a half...This is absolutely unprecedented in our lifetime."

Where does he get these figures? By what measurement? I don't doubt the figure is that large, but it is easy to throw out big numbers like that without a proper analytical basis. I looked for the transcript to see if he provided more context in the speech, but no luck. If anyone can track this down, the comments section is yours...