This video shows the math behind the Lerner Index, which gives the relationship between price elasticity of demand and the markup of price over marginal cost. For more information and a complete listing of videos and online articles by topic or textbook chapter, see http://www.economistsdoitwithmodels.com/economics-classroom/ For t-shirts and other EDIWM items, see http://www.economistsdoitwithmodels.com/merch/ By Jodi Beggs - Economists Do It With Models http://www.economistsdoitwithmodels.com/ Facebook: http://www.facebook.com/economistsdoitwithmodels Twitter: http://www.twitter.com/jodiecongirl Tumblr: http://economistsdoitwithmodels.tumblr.com/