More than a decade after the first Internet boom, U.S. productivity growth has stagnated and the economy has been unable to break out of 2 percent expansion. This situation is testing even the most optimistic of forecasters, but in contrast to our recent guest Robert Gordon, MIT professor Erik Brynjolfsson is unbowed. Brynjolfsson -- who's also director of MIT's Initiative on the Digital Economy, and co-author of the book "The Second Machine Age" -- joins Daniel Moss and Scott Lanman to explain why he thinks the current wave of advances in technology means we don't have to worry about secular stagnation after all.