Year	Percent
1991	38.222
1992	38.018
1993	37.842
1994	37.53
1995	37.185
1996	36.834
1997	36.518
1998	36.593
1999	36.239
2000	34.793
2001	34.005
2002	32.838
2003	31.443
2004	30.133
2005	28.865
2006	27.997
2007	26.719
2008	26.108
2009	25.603
2010	25.303
2011	25.039
2012	24.781
2013	24.555
2014	24.296
2015	24.11
2016	24.001
2017	23.775
2018	23.564
2019	23.348
2020	23.103
2021	22.879
2022	22.633