Year	Percent
1991	45.918
1992	43.083
1993	40.925
1994	41.595
1995	41.707
1996	41.842
1997	41.187
1998	40.318
1999	40.121
2000	38.043
2001	36.758
2002	36.225
2003	36.41
2004	34.93
2005	33.418
2006	32.824
2007	32.636
2008	31.11
2009	29.615
2010	29.105
2011	26.632
2012	26.043
2013	25.098
2014	21.298
2015	18.873
2016	18.773
2017	18.841
2018	18.561
2019	18.248
2020	17.882
2021	17.498
2022	17.059