Year	Percent
1965	6.85349
1966	6.77037
1967	9.7468
1968	9.49477
1969	9.38633
1970	8.59482
1971	8.68196
1972	9.42731
1973	8.72951
1974	9.20502
1975	18.96911
1976	18.89446
1977	21.2062
1978	22.12214
1979	18.73765
1980	21.54829
1981	20.79256
1982	21.7343
1983	24.08386
1984	23.23818
1985	22.68581
1986	23.08391
1987	17.83143
1988	17.13684
1989	17.42015
1990	24.62417
1991	20.94005
1992	18.70344
1993	18.33483
1994	21.17008
1995	15.97119
1996	18.08581
1997	18.61007
1998	18.70272
1999	17.60257
2000	15.81381
2001	15.51615
2002	15.1301
2003	12.79314
2004	12.9375
2005	13.46614
2006	13.34631
2007	15.01238
2008	14.60792
2009	14.15585
2010	14.81676
2011	16.52978
2012	16.52895
2013	17.19962
2014	17.18369
2015	16.97751
2016	16.36962
2017	15.76516