Year	Percent
1990	48.44
1991	48.77
1992	49.76
1993	50.66
1994	52.24
1995	52.9
1996	53.51
1997	53.03
1998	53.91
1999	54.31
2000	53.85
2001	52.8
2002	51.61
2003	50.7
2004	49.83
2005	48.41
2006	46.95
2007	45.53
2008	44.1
2009	42.66
2010	41.73
2011	42.32
2012	40.76
2013	41.46
2014	41.3
2015	44.11
2016	42.79
2017	42.34
2018	38.64
2019	41.51
2020	39.63