Year	Percent
1990	26.11
1991	26.23
1992	27.16
1993	26.44
1994	27.27
1995	27.77
1996	28.39
1997	29.52
1998	27.38
1999	28.61
2000	29.37
2001	29.74
2002	30.47
2003	28.51
2004	29.88
2005	29.94
2006	30.46
2007	31.29
2008	30.73
2009	30.29
2010	29.64
2011	29.76
2012	30.73
2013	31.19
2014	31.78
2015	32.64
2016	32.48
2017	33.09
2018	33.58
2019	35.22