Year	Percent
1991	43.96
1992	47.61
1993	45.4
1994	42.73
1995	41.03
1996	37.98
1997	32.84
1998	29.36
1999	34.21
2000	34.6
2001	33.52
2002	34.51
2003	32.61
2004	32.73
2005	33.31
2006	32.92
2007	34.15
2008	36.43
2009	34.79
2010	34.45
2011	35.03
2012	33.52
2013	33.95
2014	32.74
2015	31.23
2016	30.76
2017	28.95
2018	27.49
2019	27.25