Year	Percent
1991	14.82013
1992	14.41104
1993	14.09226
1994	13.79408
1995	14.49004
1996	13.0431
1997	12.5356
1998	11.90237
1999	11.19965
2000	11.42837
2001	11.73956
2002	10.79911
2003	12.77014
2004	10.06543
2005	10.02147
2006	9.7233
2007	9.43202
2008	9.14397
2009	9.03883
2010	8.63004
2011	7.72599
2012	7.66436
2013	7.40667
2014	7.1528
2015	6.90878
2016	6.66774
2017	6.43437
2018	6.20344
2019	5.96547