Year	Percent
1990	29.3
1991	29.18
1992	28.53
1993	28.66
1994	29.1
1995	27.18
1996	27.49
1997	28.22
1998	28.99
1999	30.79
2000	30.56
2001	31.35
2002	31.24
2003	27.92
2004	26.18
2005	24.61
2006	24
2007	23.88
2008	24.62
2009	27.69
2010	29.56
2011	28.65
2012	28.31
2013	29.12
2014	30.12
2015	31.26
2016	31.83
2017	34.31
2018	35.22
2019	36.1