Year	Percent
1991	18.075
1992	17.8
1993	17.579
1994	17.184
1995	16.776
1996	16.409
1997	15.819
1998	15.544
1999	14.862
2000	14.213
2001	14.228
2002	14.109
2003	13.883
2004	13.633
2005	13.301
2006	12.946
2007	12.428
2008	12.33
2009	12.728
2010	12.547
2011	12.058
2012	11.95
2013	11.854
2014	11.992
2015	11.786
2016	11.737
2017	11.798
2018	11.59
2019	11.368
2020	11.174
2021	10.991
2022	10.82