Year	Percent
1960	66.57676
1961	65.75729
1962	67.09884
1963	69.90174
1964	72.24262
1965	74.23672
1966	75.1345
1967	71.8686
1968	77.5062
1969	84.82234
1970	85.70849
1971	85.47331
1972	84.58485
1973	92.77206
1974	103.33905
1975	90.23963
1976	95.7192
1977	93.58896
1978	91.91217
1979	100.57717
1980	106.97351
1981	112.17904
1982	119.43441
1983	122.36267
1984	128.11162
1985	126.73925
1986	113.88995
1987	110.74405
1988	113.11726
1989	120.22101
1990	115.00462
1991	112.6363
1992	105.14349
1993	108.70924
1994	113.82606
1995	118.52132
1996	122.70871
1997	132.04201
1998	134.65174
1999	132.19006
2000	153.79358
2001	155.15037
2002	160.10115
2003	153.77971
2004	159.74952
2005	168.60035
2006	175.29442
2007	178.56554
2008	180.89101
2009	149.31066
2010	165.20995
2011	178.86138
2012	177.76575
2013	176.69281
2014	174.64233
2015	169.66852
2016	164.83329
2017	168.99913