Year	Percent
1990	28.29
1991	28.11
1992	27.92
1993	27.9
1994	27.78
1995	28.48
1996	29.18
1997	29.88
1998	30.71
1999	31.55
2000	32.4
2001	32.58
2002	32.75
2003	32.93
2004	33.11
2005	33.29
2006	33.47
2007	33.64
2008	33.81
2009	33.98
2010	34.15
2011	34.32
2012	34.47
2013	40.54
2014	35.33
2015	30.42
2016	26.13
2017	32.3
2018	39.35
2019	39.41