If you would use the main event field size as an indicator you would just get 3/4x growth.
Below are the WSOP ME number-of-entrants stats, from Wiki, supporting what you said. (See 2003 to 2004.)
1994 268
1995 273
1996 295
1997 312
1998 350
1999 393
2000 512
2001 613
2002 631
2003 839
2004 2576
2005 5619
2006 8773
2007 6358
2008 6844
2009 6494
2010 7319