Year	Percent
1983	5.7541
1984	5.6597
1985	5.8261
1986	5.5412
1987	6.0946
1988	5.2747
1989	4.538
1990	4.0393
1991	4.4244
1992	4.9109
1993	6.4606
1994	7.5441
1995	7.053
1996	8.242
1997	9.3083
1998	9.2892
1999	8.5594
2000	7.6396
2001	7.7673
2002	8.696
2003	10.1807
2004	11.2509
2005	11.3943
2006	10.3136
2007	8.5447
2008	7.4212
2009	8.1037
2010	7.3662
2011	6.0333
2012	5.5526
2013	5.5028
2014	5.2835
2015	4.974
2016	4.4507
2017	4.1171