Year	Percent
1975	67.56845
1976	66.99956
1977	59.06764
1978	60.97107
1979	66.03079
1980	70.45156
1981	64.91745
1982	60.52843
1983	58.85992
1984	56.05632
1985	57.45543
1986	50.26572
1987	53.88498
1988	56.68261
1989	66.57664
1990	68.52468
1991	74.06478
1992	77.74086
1993	83.79922
1994	82.92262
1995	79.31053
1996	92.2871
1997	94.53362
1998	87.77823
1999	80.75589
2000	81.31709
2001	82.95995
2002	86.3401
2003	95.86834
2004	110.31943
2005	111.80626
2006	110.59269
2007	120.63238
2008	131.93218
2009	134.88604
2010	130.78556
2011	144.01167
2012	153.50091
2013	158.41785
2014	153.54578
2015	157.34288
2016	159.64371
2017	164.15078