Year	Percent
1981	21.17909
1982	21.09844
1983	3.77684
1984	10.19795
1985	5.57351
1986	15.6228
1987	24.44386
1988	18.34684
1989	14.49246
1990	15.93665
1991	18.1122
1992	20.88792
1993	20.26962
1994	15.46091
1995	21.09606
1996	19.65672
1997	22.72981
1998	24.28889
1999	23.53199
2000	16.02216
2001	13.40724
2002	18.28065
2003	15.52906
2004	13.02403
2005	16.71284
2006	23.1089
2007	22.7931
2008	21.17313
2009	27.75607
2010	28.03989
2011	28.92569
2012	31.02642
2013	28.0938
2014	32.91321
2015	40.17234
2016	74.70007