Year	Percent
1991	28.978
1992	31.343
1993	32.241
1994	30.964
1995	29.527
1996	29.198
1997	26.781
1998	25.404
1999	24.149
2000	25.064
2001	25.84
2002	25.431
2003	23.688
2004	23.8
2005	23.113
2006	21.782
2007	20.937
2008	20.425
2009	20.099
2010	20.103
2011	19.837
2012	19.197
2013	18.462
2014	17.753
2015	17.654
2016	16.861
2017	17.111
2018	17.005
2019	16.927
2020	16.871
2021	16.833
2022	16.794