Year	Percent
1991	40.928
1992	40.511
1993	39.684
1994	38.986
1995	38.758
1996	39.661
1997	39.956
1998	42.66
1999	42.024
2000	41.133
2001	41.707
2002	42.039
2003	41.718
2004	41.482
2005	41.897
2006	41.818
2007	41.946
2008	41.614
2009	41.106
2010	40.174
2011	40.232
2012	39.082
2013	39.09
2014	40.079
2015	39.908
2016	39.921
2017	39.738
2018	39.56
2019	39.436
2020	39.276
2021	39.12
2022	38.966