Year	Percent
1965	13.9236
1966	8.75669
1967	6.95246
1968	7.50035
1969	10.21916
1970	8.30292
1971	9.12956
1972	7.91783
1973	10.37215
1974	10.5481
1975	13.36673
1976	14.1773
1977	14.31713
1978	15.47233
1979	15.96669
1980	18.73153
1981	19.61768
1982	18.80728
1983	21.31517
1984	19.4491
1985	19.99957
1986	20.30274
1987	20.90661
1988	22.38187
1989	22.28332
1990	21.66145
1991	23.1843
1992	25.73569
1993	28.75662
1994	31.43813
1995	34.51736
1996	35.64019
1997	37.7077
1998	33.88755
1999	29.71851
2000	32.42659
2001	33.23911
2002	28.49359
2003	28.54802
2004	29.46459
2005	29.47926
2006	31.3154
2007	31.72361
2008	33.26039
2009	34.66009
2010	36.40237
2011	32.92422
2012	33.58431
2013	37.45693
2014	40.75011
2015	41.47333
2016	39.38328
2017	42.01652