Year	Percent
1970	7.9325
1971	7.6188
1972	8.03168
1973	6.50114
1974	5.70794
1975	4.56233
1976	10.3547
1977	18.44712
1978	25.72432
1979	49.03003
1980	32.69865
1981	31.53298
1982	40.03671
1983	54.84469
1984	50.02989
1985	59.38964
1986	54.05678
1987	50.98291
1988	43.05892
1989	38.78954
1990	35.43577
1991	37.28377
1992	36.03802
1993	35.87168
1994	35.76051
1995	42.67645
1996	45.75428
1997	71.34211
1998	50.76326
1999	60.14786
2000	80.87581
2001	89.71034
2002	98.18928
2003	117.85265
2004	102.49789
2005	102.21272
2006	96.41553
2007	94.94446
2008	105.92939
2009	105.01426
2010	105.12405
2011	91.75421
2012	82.16562
2013	83.4536
2014	82.23713
2015	80.78217
2016	80.39192