Year	Percent
1991	36.687
1992	36.736
1993	36.479
1994	39.475
1995	39.368
1996	39.117
1997	39.604
1998	38.687
1999	40.099
2000	39.793
2001	39.055
2002	38.463
2003	38.788
2004	39.008
2005	38.565
2006	38.201
2007	38.577
2008	38.897
2009	36.472
2010	37.612
2011	37.652
2012	37.925
2013	37.46
2014	37.097
2015	35.796
2016	35.822
2017	36.212
2018	36.693
2019	35.978
2020	35.424
2021	34.508
2022	33.971