Year	Percent
1991	35.753
1992	35.771
1993	35.841
1994	35.347
1995	34.964
1996	34.93
1997	34.946
1998	34.921
1999	34.681
2000	34.25
2001	34.292
2002	33.497
2003	32.381
2004	31.371
2005	30.686
2006	30.191
2007	29.973
2008	28.479
2009	26.717
2010	24.505
2011	22.601
2012	20.873
2013	20.846
2014	20.782
2015	20.616
2016	20.838
2017	20.819
2018	20.894
2019	20.999
2020	21.06
2021	21.064
2022	21.029