Year	Percent
1976	13.0363
1977	14.5212
1978	14.6401
1979	12.9178
1980	13.386
1981	13.7093
1982	20.6536
1983	21.7852
1984	19.1013
1985	17.3399
1986	15.9984
1987	14.3419
1988	12.4
1989	12.182
1990	13.5362
1991	18.5323
1992	19.7337
1993	19.6893
1994	17.9016
1995	16.3362
1996	16.8784
1997	17.1279
1998	16.5484
1999	15.3015
2000	13.8423
2001	14.5001
2002	15.3893
2003	15.3446
2004	14.9685
2005	14.1103
2006	12.8496
2007	12.2658
2008	13.0323
2009	18.3483
2010	17.2702
2011	16.0981
2012	16.0885
2013	15.1838
2014	14.9821
2015	15.0418
2016	14.8182
2017	13.2536