Year	Percent
1966	12.82206
1967	13.06437
1968	13.26519
1969	13.63398
1970	14.58783
1971	14.58106
1972	15.14636
1973	15.999
1974	14.15073
1975	14.12914
1976	14.31192
1977	15.18971
1978	15.21362
1979	15.21752
1980	14.25201
1981	12.56034
1982	11.90219
1983	11.98456
1984	11.50594
1985	11.86418
1986	11.57367
1987	11.96124
1988	11.67371
1989	13.45002
1990	11.70106
1991	12.30783
1992	11.49604
1993	11.09111
1994	9.12142
1995	8.5719
1996	10.58203
1997	12.43432
1998	12.53133
1999	12.48633
2000	12.89601
2001	13.45337
2002	13.57297
2003	14.09323
2004	14.49976
2005	14.31612
2006	14.75737
2007	14.80716
2008	14.55562
2009	14.68755
2010	14.63522
2011	14.63632
2012	14.66708
2013	14.74121
2014	14.67533
2015	14.41368
2016	16.73232