Year	Percent
1991	21.67751
1992	21.40424
1993	21.15327
1994	20.71097
1995	20.29585
1996	19.85345
1997	19.98794
1998	17.08727
1999	17.53938
2000	15.6023
2001	14.3927
2002	15.22071
2003	14.26452
2004	14.236
2005	13.6829
2006	13.69092
2007	12.85393
2008	12.68069
2009	13.12791
2010	12.41711
2011	12.04019
2012	11.3592
2013	11.08169
2014	11.25941
2015	9.71531
2016	8.92701
2017	9.57713
2018	9.36373
2019	8.71323