Year	Percent
1990	44.56
1991	45.44
1992	45.37
1993	46.88
1994	46.41
1995	45.93
1996	46.89
1997	47.83
1998	47.82
1999	47.67
2000	46.34
2001	46.64
2002	46.94
2003	47
2004	46.87
2005	47.27
2006	47.55
2007	46.85
2008	45.89
2009	45.25
2010	44.61
2011	43.91
2012	43.19
2013	42.44
2014	41.64
2015	40.79
2016	40.67
2017	40.47
2018	40.18
2019	39.8
2020	37.94