Year	Percent
1991	31.681
1992	31.729
1993	31.223
1994	31.172
1995	30.143
1996	29.541
1997	29.542
1998	29.18
1999	28.681
2000	27.609
2001	26.711
2002	26.943
2003	27.052
2004	27.017
2005	26.899
2006	27.284
2007	26.145
2008	25.415
2009	25.279
2010	24.63
2011	23.647
2012	23.398
2013	23.771
2014	23.913
2015	23.921
2016	23.594
2017	23.631
2018	23.554
2019	23.42
2020	23.242
2021	23.069
2022	22.82