Year	Percent
1991	42.11
1992	41.04
1993	38.84
1994	38.06
1995	38.66
1996	39.19
1997	40.31
1998	41.63
1999	43.73
2000	45.55
2001	46.75
2002	47.74
2003	48.68
2004	49.56
2005	51.66
2006	52.76
2007	53.32
2008	52.22
2009	48.5
2010	47.52
2011	46.61
2012	44.6
2013	43.59
2014	44.28
2015	45.59
2016	46.86
2017	48
2018	48.95
2019	49.56
2020	47.44