iTunes 3 billion songs purchased on a graph

It took a little less than a year to go from 1 billion to 2 billion songs sold on iTunes.  It took a little over six months to go from 2 billion to 3 billion songs sold.  Will we see 4 billion songs sold by the end of the year?

Date

Songs Purchased (millions)

Source

05/15/2003 1 Apple
06/23/2003 5 Apple
09/8/2003 10 Apple
12/15/2003 25 Apple
03/15/2004 50 Apple
07/12/2004 100 CNN
12/16/2004 200 Apple
07/18/2005 500 Apple
02/24/2006 1000 Apple
01/09/2007 2000 Apple
07/31/2007 3000 Apple

Analysis elsewhere:

graph created using NCES Create a Graph

links for 2007-07-31

links for 2007-07-30

links for 2007-07-28