Year	Percent
1991	29.699
1992	33.296
1993	34.237
1994	33.441
1995	32.302
1996	31.956
1997	28.76
1998	27.486
1999	26.848
2000	27.414
2001	27.985
2002	28.256
2003	27.007
2004	26.531
2005	25.782
2006	24.463
2007	23.496
2008	22.964
2009	22.782
2010	22.986
2011	22.874
2012	22.403
2013	21.838
2014	21.361
2015	21.242
2016	20.728
2017	21.161
2018	21.056
2019	20.982
2020	20.929
2021	20.895
2022	20.86