Year	Percent
1970	99.06141
1971	99.50264
1972	96.81367
1973	110.03492
1974	98.13499
1975	135.65048
1976	132.30803
1977	82.65577
1978	83.452
1979	83.98079
1980	101.89699
1981	91.10921
1982	74.661
1983	81.08062
1984	75.07942
1985	66.94513
1986	70.247
1987	76.04529
1988	73.00338
1989	70.77455
1990	66.11081
1991	65.2751
1992	52.73836
1993	58.07527
1994	54.04096
1995	50.71744
1996	53.64824
1997	52.62603
1998	48.49641
1999	46.41211
2000	54.45702
2001	47.71426
2002	49.67708
2003	51.51865
2004	44.35834
2005	45.06461
2006	45.46224
2007	45.40733
2008	50.90626
2009	46.10395
2010	42.81254
2011	38.70565
2012	36.98119
2013	38.64501
2014	38.36959
2015	40.10935
2016	42.25169
2017	37.00358