The Wharton researchers also disagree with Anderson's theory and its implicit challenge to the Pareto principle, or so-called 80-20 rule, which in this case would state that 20% of the movie titles generate 80% of sales. Anderson argues that as demand shifts down the tail, the effect would diminish. Using Netflix data, Netessine and Tan show the opposite -- an even stronger effect, with demand for the top 20% of movies increasing from 86% in 2000 to 90% in 2005.
Anderson did his own analysis using the Wharton data and found lower demand for the top 500 products and more interest in the middle part of the curve. He also points out that a Long Tail adding up to 15% of total demand came from titles beyond the top 3,000 -- the amount typically stocked in a video store.