Year	Percent
1991	25.326
1992	23.782
1993	20.414
1994	19.72
1995	19.867
1996	19.13
1997	20.05
1998	21.124
1999	23.831
2000	26.838
2001	27.459
2002	27.789
2003	28.675
2004	29.139
2005	32.743
2006	34.334
2007	33.733
2008	32.369
2009	26.382
2010	24.003
2011	21.669
2012	17.964
2013	16.082
2014	15.923
2015	17.286
2016	17.329
2017	19.461
2018	21.089
2019	21.688
2020	21.879
2021	22.025
2022	22.197