Year	Percent
1991	27.823
1992	27.786
1993	26.923
1994	26.515
1995	26.338
1996	26.227
1997	25.456
1998	24.728
1999	24.907
2000	24.202
2001	23.525
2002	23.645
2003	23.375
2004	22.811
2005	22.151
2006	21.691
2007	21.174
2008	20.24
2009	19.303
2010	18.796
2011	18.228
2012	17.59
2013	17.051
2014	16.876
2015	16.522
2016	16.383
2017	16.33
2018	16.311
2019	16.293
2020	16.274
2021	16.256
2022	16.239