Year	Percent
1990	32.14
1991	32.18
1992	30.62
1993	29.26
1994	28.08
1995	37.33
1996	40.82
1997	44.47
1998	41.25
1999	38.06
2000	45.42
2001	47.94
2002	43.05
2003	45.63
2004	46.12
2005	45.65
2006	46.92
2007	47.74
2008	51.1
2009	50.66
2010	51.78
2011	50.25
2012	51.11
2013	49.23
2014	49.81
2015	50.55
2016	49.32
2017	50.12
2018	51.52
2019	52.72