\section{The Grateful Dead Usage Statistics\label{sec:usage}}

The online music service last.fm tracks how registered members enjoy music by what songs they play on Internet radio or through a computer music player plug-in.  The last.fm service maintains a database of the listening behavior of its registered members. From this database, the last.fm service is able to recommend songs and artists to its members based on the listening behavior of similar members.  This service is analogous to Amazon.com using historical purchasing behavior to recommend products to customers. Table \ref{tab:usage} lists the top $15$ Grateful Dead songs listened to by last.fm members. These data were gathered from August 2005 to October 2007 and include 2,616,990 unique listening events.  Figure 3 presents a histogram of the listening counts of songs. In summary, similar to the concert behavior of the Grateful Dead, many songs were listened to a few times and a few songs were listened to many times.