Year	Percent
1979	11.7274
1980	11.352
1981	10.1808
1982	13.2794
1983	19.3987
1984	17.5159
1985	15.5612
1986	15.2676
1987	15.0387
1988	13.3736
1989	10.6587
1990	13.2296
1991	18.5607
1992	20.7651
1993	19.7153
1994	17.4235
1995	15.5373
1996	16.4096
1997	16.9305
1998	15.3153
1999	13.7452
2000	12.8938
2001	14.5938
2002	13.7916
2003	12.6078
2004	11.8464
2005	10.8855
2006	10.5516
2007	9.4763
2008	9.017
2009	12.4821
2010	11.9466
2011	11.9383
2012	12.456
2013	13.0355
2014	14.1024
2015	14.2346
2016	13.818
2017	13.6679