Year	Percent
1991	23.618
1992	29.484
1993	29.82
1994	30.525
1995	29.901
1996	30.212
1997	29.897
1998	29.296
1999	29.273
2000	28.446
2001	27.934
2002	28.103
2003	27.487
2004	27.6
2005	27.106
2006	28.365
2007	30.065
2008	33.172
2009	33.278
2010	33.868
2011	34.033
2012	34.2
2013	34.933
2014	34.953
2015	35.233
2016	35.458
2017	35.234
2018	35.094
2019	34.854
2020	34.677
2021	34.485
2022	34.334