Year	Percent
1991	36.581
1992	36.216
1993	36.101
1994	35.465
1995	34.751
1996	33.003
1997	32.817
1998	32.755
1999	31.923
2000	42.477
2001	29.447
2002	28.521
2003	28.501
2004	27.434
2005	25.346
2006	26.111
2007	26.307
2008	27.186
2009	37.951
2010	37.234
2011	24.176
2012	23.568
2013	22.391
2014	20.49
2015	20.117
2016	20.047
2017	20.066
2018	19.948
2019	19.818
2020	19.689
2021	19.545
2022	19.391