Year	Percent
1991	39.605
1992	38.677
1993	40.304
1994	39.579
1995	39.341
1996	38.626
1997	38.382
1998	37.042
1999	37.95
2000	38.627
2001	36.465
2002	36.114
2003	35.599
2004	34.522
2005	33.972
2006	33.544
2007	33.251
2008	32.934
2009	32.943
2010	32.214
2011	32.233
2012	32.361
2013	30.365
2014	28.436
2015	28.526
2016	29.065
2017	29.758
2018	29.607
2019	29.361
2020	29.046
2021	28.744
2022	28.431