Year	Percent
1991	52.52
1992	51.81
1993	50.63
1994	49.62
1995	49.02
1996	48.26
1997	47.91
1998	47.71
1999	47.2
2000	46.33
2001	45.61
2002	44.39
2003	42.98
2004	41.71
2005	40.69
2006	39.49
2007	38.47
2008	37.45
2009	36.07
2010	34.92
2011	34.25
2012	33.63
2013	33.07
2014	32.58
2015	32.07
2016	31.82
2017	31.5
2018	31.15
2019	30.83