Year	Percent
1991	41.269
1992	40.682
1993	38.972
1994	38.308
1995	38.567
1996	37.814
1997	38.652
1998	39.461
1999	40.122
2000	40.221
2001	41.403
2002	41.184
2003	41.577
2004	41.435
2005	41.052
2006	41.58
2007	41.399
2008	39.961
2009	35.823
2010	33.557
2011	32.121
2012	30.272
2013	29.114
2014	28.575
2015	29.155
2016	28.841
2017	28.813
2018	28.681
2019	28.524
2020	28.375
2021	28.23
2022	28.153