Year	Percent
1991	39.347
1992	43.5
1993	41.605
1994	38.605
1995	36.21
1996	34.293
1997	30.286
1998	26.829
1999	28.852
2000	30.831
2001	29.66
2002	30.471
2003	29.507
2004	29.297
2005	30.249
2006	30.01
2007	31.186
2008	32.231
2009	31.42
2010	30.641
2011	31.119
2012	29.666
2013	30.054
2014	28.999
2015	27.719
2016	27.06
2017	26.098
2018	25.009
2019	24.031
2020	23.251
2021	22.706
2022	22.455