Year	Percent
1991	27.572
1992	27.094
1993	27.088
1994	26.531
1995	25.808
1996	24.334
1997	24.344
1998	24.853
1999	24.65
2000	23.897
2001	23.372
2002	23.827
2003	23.65
2004	23.341
2005	22.732
2006	21.456
2007	20.564
2008	19.353
2009	18.825
2010	17.458
2011	16.887
2012	16.758
2013	17.706
2014	17.213
2015	17.114
2016	17.133
2017	16.288
2018	15.815
2019	15.169
2020	14.594
2021	13.972
2022	13.547