Year	Percent
1991	38.82
1992	41.23
1993	34.7
1994	33.18
1995	32.9
1996	30.99
1997	33.14
1998	32.7
1999	32.09
2000	30.16
2001	28.52
2002	28.65
2003	31.43
2004	29.18
2005	32.56
2006	35.72
2007	38.61
2008	37.54
2009	27.88
2010	25.79
2011	26.16
2012	28.85
2013	30.2
2014	32.67
2015	35.17
2016	34.4
2017	34.92
2018	34.74
2019	31.75