Year	Percent
1991	19.093
1992	18.824
1993	17.704
1994	15.245
1995	15.119
1996	17.739
1997	18.343
1998	20.25
1999	21.141
2000	22.114
2001	21.889
2002	20.515
2003	19.503
2004	19.224
2005	18.745
2006	18.267
2007	17.8
2008	17.733
2009	15.991
2010	15.697
2011	16.159
2012	15.458
2013	15.978
2014	16.324
2015	16.47
2016	16.894
2017	16.976
2018	17.029
2019	16.978
2020	16.806
2021	16.7
2022	16.642