Year	Percent
1991	12.79
1992	13.13
1993	13.07
1994	12.93
1995	12.57
1996	12.14
1997	12.08
1998	11.66
1999	12.07
2000	11.92
2001	11.97
2002	12.01
2003	12.1
2004	12.1
2005	12.08
2006	14.14
2007	15.82
2008	16.12
2009	15.7
2010	15.23
2011	14.98
2012	15.62
2013	15.92
2014	19.33
2015	19.23
2016	21.4
2017	21.79
2018	23.66
2019	27.75