Year	Percent
1991	35.38
1992	36.02
1993	32.17
1994	31.23
1995	31.95
1996	28.24
1997	28.79
1998	33.21
1999	34.39
2000	32.43
2001	31.28
2002	29.39
2003	27.14
2004	23.55
2005	21.85
2006	21.39
2007	20.67
2008	19.66
2009	17.5
2010	17.57
2011	17.53
2012	18.17
2013	20.05
2014	23.62
2015	25.87
2016	28.45
2017	29.28
2018	29.07
2019	28.38