Year	Percent
1991	49.295
1992	50.182
1993	51.871
1994	49.788
1995	48.584
1996	47.014
1997	46.664
1998	46.642
1999	45.808
2000	44.653
2001	43.828
2002	39.005
2003	39.635
2004	38.933
2005	40.627
2006	40.601
2007	40.292
2008	39.691
2009	39.57
2010	39.775
2011	39.212
2012	38.264
2013	37.596
2014	39.325
2015	41.282
2016	41.07
2017	39.98
2018	38.418
2019	36.659
2020	34.842
2021	33.043
2022	31.338