Year	Percent
1991	32.64
1992	32.446
1993	31.998
1994	31.69
1995	31.314
1996	31.182
1997	31.012
1998	30.796
1999	30.587
2000	30.329
2001	30.388
2002	30.392
2003	30.425
2004	30.433
2005	28.92
2006	27.447
2007	26.027
2008	24.672
2009	23.366
2010	22.123
2011	20.982
2012	19.871
2013	18.809
2014	19.073
2015	19.103
2016	17.861
2017	17.518
2018	17.188
2019	16.872
2020	16.576
2021	16.295
2022	16.029