Year	Percent
1990	34.98
1991	32.4
1992	31.87
1993	31.35
1994	30.84
1995	30.31
1996	29.78
1997	29.12
1998	28.44
1999	27.75
2000	27.04
2001	26.3
2002	25.56
2003	24.82
2004	24.08
2005	23.35
2006	21.66
2007	20.02
2008	17.83
2009	18.25
2010	15.69
2011	14.85
2012	14.06
2013	13.31
2014	12.58
2015	12.92
2016	13.16
2017	12.89
2018	13.19
2019	14.41