Year	Percent
1980	33.16855
1981	26.98785
1982	31.38391
1983	30.26402
1984	44.9604
1985	32.79221
1986	23.58806
1987	25.24604
1988	21.83475
1989	17.39514
1990	19.66683
1991	13.24142
1992	20.52286
1993	19.30405
1994	20.68364
1995	19.45699
1996	19.42057
1997	15.84775
1998	17.95431
1999	14.95982
2000	6.25768
2001	10.34081
2002	14.32151
2003	11.12762
2004	10.40288
2005	10.56249
2006	11.26611
2007	11.06705
2008	19.76711
2009	16.8127
2010	14.74846
2011	15.58846
2012	17.67218
2013	21.76752
2014	27.35829
2015	18.4
2016	20.9
2017	21.2