Year	Percent
1990	15.03
1991	16.39
1992	17.76
1993	19.13
1994	20.49
1995	21.86
1996	23.22
1997	24.59
1998	25.96
1999	27.32
2000	28.69
2001	30.05
2002	31.42
2003	32.79
2004	34.15
2005	35.52
2006	36.89
2007	38.25
2008	39.62
2009	40.98
2010	42.35
2011	42.35
2012	42.35
2013	42.35
2014	42.35
2015	42.35