Year	Percent
1990	45.15
1991	45.2
1992	45.31
1993	45.48
1994	45.7
1995	45.95
1996	46.09
1997	46.29
1998	46.55
1999	46.87
2000	47.23
2001	47.55
2002	47.93
2003	48.37
2004	48.85
2005	49.36
2006	49.8
2007	50.22
2008	50.62
2009	51.01
2010	51.39
2011	51.73
2012	52.01
2013	52.23
2014	52.38
2015	52.47
2016	52.61
2017	52.72
2018	52.79
2019	52.8