Year	Percent
1991	21.399
1992	22.438
1993	24.254
1994	26.149
1995	25.847
1996	24.207
1997	20.848
1998	25.029
1999	24.266
2000	24.329
2001	22.126
2002	23.521
2003	21.873
2004	21.65
2005	20.074
2006	18.966
2007	20.349
2008	20.586
2009	18.317
2010	18.395
2011	18.577
2012	18.367
2013	17.501
2014	17.967
2015	19.501
2016	17.053
2017	17.136
2018	16.978
2019	16.838
2020	16.681
2021	16.568
2022	16.413