Year	Percent
1976	1.96
1977	1.14
1978	1.76
1980	2.24
1982	3.36
1985	2.01
1986	2.56
1987	2.43
1988	2.71
1990	2.64
1991	2.9
1992	2.82
1996	5.43
1998	6.12
1999	6.84
2000	6.706
2001	7.3731
2002	7.8506
2003	8.308
2004	9.1771
2005	10.0649
2006	9.2858
2007	9.906
2008	8.1014
2009	6.6964
2010	6.3912
2011	5.5653
2012	4.7842
2013	4.2662
2014	3.8833
2015	4.4297
2016	3.8655
2017	3.922