There is a great deal of debate within the Marxist left about whether the economic crisis is the result of the long-term ill health of the so-called "real economy" or if the system crashed out of its inherent volatility. Noted historian Robert Brenner argues that it has roots in an extended period of stagnation, which he elucidated in a talk at the Berkeley Sociology Colloquium titled "Prosperity and Crisis in the World Economy: Yesterday, Today, and Tomorrow."