Year	Percent
1990	52.59
1991	52.87
1992	53.28
1993	53.79
1994	53.91
1995	53.7
1996	53.89
1997	53.67
1998	53.45
1999	53.43
2000	53.25
2001	49.83
2002	46.39
2003	42.98
2004	39.62
2005	36.35
2006	33.2
2007	30.19
2008	27.33
2009	24.65
2010	22.14
2011	22.14
2012	22.19
2013	22.23
2014	22.38
2015	22.47
2016	22.5
2017	22.52
2018	22.49
2019	22.53