Year	Percent
1991	44.23
1992	45.6
1993	44.53
1994	44.32
1995	42.26
1996	39.67
1997	36.25
1998	35.26
1999	29.78
2000	30.17
2001	27.78
2002	25.21
2003	29.41
2004	29.6
2005	30.82
2006	31.96
2007	35.02
2008	37.2
2009	29.27
2010	25.85
2011	31.21
2012	32.46
2013	32.16
2014	33.4
2015	36.63
2016	38.11
2017	41.17
2018	42.29
2019	39.38