Year	Percent
1960	26.27564
1961	27.21632
1962	27.92604
1963	28.99444
1964	28.81101
1965	31.70732
1966	29.26829
1967	24.61385
1968	23.05263
1969	22.77228
1970	24.65555
1971	33.14978
1972	37.37215
1973	38.83151
1974	40.9233
1975	43.59414
1976	50.3864
1977	50.90072
1978	52.06054
1979	54.12302
1980	53.05924
1981	49.70506
1982	54.56198
1983	62.08345
1984	60.81127
1985	66.29105
1986	68.33085
1987	75.12957
1988	70.52194
1989	59.2246
1990	55.05541
1991	53.02951
1992	48.17956
1993	47.0958
1994	47.8224
1995	50.8365
1996	53.82844
1997	60.88074
1998	49.28917
1999	55.19727
2000	51.83181
2001	48.65761
2002	52.15743
2003	48.82686
2004	49.61379
2005	52.92355
2006	52.25447
2007	54.51608
2008	45.67397
2009	34.80095
2010	43.63546
2011	48.89644
2012	48.35909
2013	61.51249
2014	60.83019
2015	52.18402
2016	55.10972