Year	Percent
1997	0.14704
1998	0.23867
1999	0.3483
2000	0.60782
2001	1.11028
2002	1.53495
2003	1.66733
2004	1.86454
2005	2.48709
2006	6.30739
2010	4.4582
2011	4.11637