Year	Percent
1991	45.796
1992	44.879
1993	44.897
1994	44.505
1995	43.777
1996	45.306
1997	45.059
1998	45.039
1999	40.688
2000	39.818
2001	39.311
2002	39.46
2003	38.813
2004	39.375
2005	39.498
2006	39.411
2007	38.256
2008	37.74
2009	37.77
2010	37.238
2011	36.119
2012	35.588
2013	34.115
2014	33.336
2015	34.201
2016	33.68
2017	35.478
2018	34.606
2019	33.694
2020	32.851
2021	32.053
2022	31.23