Year	Percent
1991	51.6
1992	48.79
1993	45.29
1994	42.25
1995	37.84
1996	36.47
1997	34.13
1998	32.5
1999	30.9
2000	31.83
2001	32.08
2002	32.24
2003	26.98
2004	23.41
2005	24.98
2006	23.78
2007	22.77
2008	24.53
2009	26.97
2010	21.51
2011	20.77
2012	22.12
2013	22.38
2014	21.39
2015	29.2
2016	25.17
2017	26.21
2018	28.46
2019	28.94