Majka Baur from “Student Reporter” interviewed me during the World Resources Forum 2011 about the core questions regarding resource efficiency:

The successor to “Factor Four” (first published in 1997) has been published by Earthscan in December.
Factor Five
Transforming the Global Economy through 80% Improvements in Resource Productivity
By Ernst von Weizsäcker, Karlson ‘Charlie’ Hargroves, Michael H. Smith, Cheryl Desha and Peter Stasinopoulos
Picking up where Factor Four left off, this new book examines the past 15 years of [...]