Year	Percent
1991	38.004
1992	34.953
1993	32.315
1994	28.119
1995	29.217
1996	28.712
1997	26.817
1998	25.71
1999	25.33
2000	24.787
2001	25.851
2002	24.979
2003	24.895
2004	23.09
2005	22.062
2006	22.284
2007	21.239
2008	19.682
2009	23.88
2010	23.107
2011	22.138
2012	21.664
2013	20.47
2014	20.347
2015	20.016
2016	19.536
2017	19.233
2018	18.59
2019	17.905
2020	17.284
2021	16.678
2022	16.108