Year	Percent
1991	40.983
1992	41.107
1993	40.819
1994	45.823
1995	39.522
1996	42.349
1997	38.828
1998	38.917
1999	38.106
2000	39.783
2001	39.705
2002	39.748
2003	39.654
2004	39.657
2005	39.642
2006	39.704
2007	39.562
2008	39.631
2009	39.636
2010	39.51
2011	39.469
2012	39.5
2013	39.511
2014	39.458
2015	39.457
2016	39.499
2017	39.722
2018	39.757
2019	39.661
2020	39.558
2021	39.465
2022	39.373