Year	Percent
1991	32.991
1992	32.277
1993	31.402
1994	31.184
1995	30.884
1996	30.773
1997	30.094
1998	29.52
1999	29.49
2000	29.004
2001	28.378
2002	28.467
2003	28.019
2004	27.206
2005	26.29
2006	25.489
2007	24.928
2008	24.107
2009	23.316
2010	22.848
2011	22.304
2012	21.852
2013	21.532
2014	21.229
2015	20.959
2016	20.856
2017	20.762
2018	20.736
2019	20.71
2020	20.684
2021	20.658
2022	20.634