Year	Percent
1991	17.811
1992	17.403
1993	17.723
1994	17.051
1995	16.598
1996	17.344
1997	17.17
1998	17.053
1999	16.988
2000	16.214
2001	15.932
2002	15.953
2003	16.489
2004	15.788
2005	16.326
2006	16.089
2007	15.598
2008	15.947
2009	16.443
2010	16.426
2011	15.952
2012	15.417
2013	14.904
2014	14.822
2015	15.26
2016	20.692
2017	20.591
2018	20.577
2019	20.561
2020	20.544
2021	20.528
2022	20.512