Year	Percent
1991	36.92
1992	35.81
1993	36.48
1994	35.1
1995	34.95
1996	31.19
1997	30.09
1998	27.85
1999	27.9
2000	28.55
2001	28.62
2002	23.64
2003	27.96
2004	22.54
2005	23.74
2006	24.07
2007	24.48
2008	23.02
2009	21.29
2010	23.91
2011	24.93
2012	26.24
2013	23.87
2014	25.72
2015	27.02
2016	25.75
2017	28.77
2018	28.89
2019	27.62