Year	Percent
1991	37.48
1992	36.54
1993	35.17
1994	35.12
1995	33.07
1996	31.94
1997	30.26
1998	29.66
1999	29.12
2000	29.04
2001	29.38
2002	29.78
2003	31.17
2004	28.1
2005	27.71
2006	27.99
2007	27.96
2008	27
2009	25.66
2010	24.33
2011	23.51
2012	22.1
2013	21.21
2014	21.55
2015	22.44
2016	23.46
2017	25.76
2018	25.45
2019	27.24