Year	Percent
1991	50.786
1992	48.806
1993	47.722
1994	46.943
1995	45.799
1996	44.274
1997	44.426
1998	43.685
1999	41.298
2000	41.183
2001	40.937
2002	37.166
2003	37.743
2004	37.199
2005	37.172
2006	37.901
2007	38.145
2008	36.914
2009	35.474
2010	38.739
2011	36.186
2012	36.778
2013	36.365
2014	38.182
2015	40.821
2016	40.752
2017	40.58
2018	40.634
2019	40.596
2020	40.304
2021	40.041
2022	39.769