Year	Percent
1983	1.5452
1984	1.8773
1985	1.4739
1986	1.8742
1987	2.2907
1988	1.6208
1989	2.3832
1990	1.6644
1991	1.9873
1992	2.1466
1993	2.935
1994	3.7094
1995	4.004
1996	4.3526
1997	4.6528
1998	4.6508
1999	4.6218
2000	4.5733
2001	4.6753
2002	4.1127
2003	4.1223
2004	3.9772
2005	3.6249
2006	2.8611
2007	2.5783
2008	3.2508
2009	3.7464
2010	3.9089
2011	4.5532
2012	5.9466
2013	6.7306
2014	6.1915
2015	6.3992
2016	6.414
2017	6.3095