Year	Percent
1991	9.91609
1992	9.69421
1993	9.43921
1994	8.69407
1995	7.9789
1996	7.3006
1997	7.08514
1998	6.85108
1999	6.62712
2000	6.39109
2001	6.69694
2002	7.00767
2003	7.32929
2004	7.64231
2005	7.93436
2006	8.20817
2007	8.43294
2008	8.6129
2009	6.79064
2010	5.15419
2011	5.08458
2012	5.02488
2013	4.86447
2014	4.68293
2015	4.57213
2016	4.46488
2017	4.27476
2018	4.02439
2019	3.88339