Year	Percent
1990	49.5
1991	51.47
1992	53.61
1993	55.92
1994	58.42
1995	56.87
1996	53.33
1997	50.14
1998	48.87
1999	47.79
2000	49.54
2001	50.97
2002	48.4
2003	48.74
2004	48.16
2005	47.21
2006	44.85
2007	42.5
2008	40.19
2009	37.91
2010	36.36
2011	37.03
2012	39.5
2013	39.29
2014	40.17
2015	40.59
2016	41.88
2017	39.91
2018	37.96
2019	38.7