Year	Percent
1966	8.17809
1967	9.18775
1968	10.59032
1969	10.04113
1970	6.88986
1971	5.5931
1972	7.2266
1973	8.12
1974	5.95711
1975	8.54502
1976	11.75146
1977	13.27857
1978	23.13292
1979	29.08967
1980	26.69548
1981	25.3339
1982	22.46033
1983	18.88316
1984	18.3134
1985	15.08618
1986	16.59925
1987	17.12583
1988	16.35596
1989	20.36526
1990	22.34319
1991	20.33775
1992	24.78933
1993	5.27776
1994	4.68549
1995	6.9037
1996	6.7792
1997	5.17517
1998	4.8844
1999	4.75505
2000	4.5625
2001	11.17274
2002	7.27833
2003	10.03889
2004	24.21694
2005	21.98428
2006	24.27717
2007	19.08952
2008	15.85759
2009	19.61396
2010	21.31924
2011	18.93923
2012	27.79466
2013	20.01844
2014	20.87963
2015	19.69877
2016	18.73018
2017	19.17098