Year	Percent
1991	40.942
1992	41.269
1993	41.276
1994	40.954
1995	41.479
1996	40.515
1997	40.335
1998	40.147
1999	40.258
2000	40.135
2001	40.127
2002	40.121
2003	39.224
2004	39.225
2005	38.647
2006	38.478
2007	38.228
2008	38.24
2009	37.988
2010	37.499
2011	46.97
2012	38.237
2013	41.546
2014	44.239
2015	40.546
2016	40.147
2017	39.659
2018	39.512
2019	39.385
2020	39.18
2021	39.049
2022	38.966