Year	Percent
1991	17.541
1992	18.574
1993	16.72
1994	16.633
1995	16.654
1996	16.612
1997	16.351
1998	16.539
1999	16.595
2000	16.37
2001	16.141
2002	16.065
2003	16.038
2004	15.459
2005	18.301
2006	18.256
2007	17.764
2008	17.691
2009	17.565
2010	17.45
2011	17.866
2012	18.024
2013	17.958
2014	18.02
2015	17.915
2016	17.332
2017	17.146
2018	17.097
2019	17.046
2020	16.994
2021	16.934
2022	16.876