Year	Percent
1981	15.27665
1982	15.37428
1983	14.91616
1984	16.78544
1985	13.9861
1986	15.80935
1987	13.49819
1988	14.28187
1989	12.26846
1990	11.32633
1991	4.90944
1992	9.60641
1993	11.16558
1994	20.28017
1995	20.44628
1996	21.26828
1997	19.79227
1998	26.57381
1999	26.03614
2000	21.18828
2001	27.52823
2002	26.41445
2003	36.90181
2004	35.0609
2005	40.30093
2006	40.90269
2007	35.9546
2008	36.49627
2009	28.62786
2010	36.51914
2011	36.84055
2012	35.28579
2013	32.18682
2014	34.12629
2015	30.9677
2016	27.23863
2017	24.15419