Year	Percent
1980	8.69932
1981	11.75808
1982	15.68627
1983	19.82775
1984	9.01891
1985	16.99782
1986	16.44038
1987	15.2452
1988	17.98498
1989	14.88241
1990	14.25214
1991	20.01149
1992	18.04053
1993	19.96999
1994	20.07343
1995	19.7634
1996	18.32368
1997	18.14295
1998	11.35431
1999	12.71137
2000	22.98912
2001	18.32186
2002	15.58691
2003	18.89897
2004	15.46927
2005	15.01236
2006	14.80495
2007	15.45789
2008	14.17027
2009	14.82402
2010	16.48143
2011	17.35161
2012	15.6861
2013	16.3206
2014	16.87471
2015	17.79042
2016	15.94211
2017	17.7