Year	Percent
1970	15.90293
1971	15.0271
1972	15.82711
1973	15.93076
1974	24.99415
1975	28.87402
1976	30.16197
1977	30.32349
1978	41.46372
1979	45.57042
1980	69.82874
1981	64.20306
1982	78.96075
1983	93.25637
1984	90.9741
1985	74.62725
1986	63.13821
1987	57.56411
1988	77.83741
1989	92.02307
1990	129.70903
1991	156.44274
1992	251.21172
1993	199.12045
1994	143.73203
1995	137.9081
1996	195.96126
1997	144.0143
1998	154.76949
1999	158.48017
2000	139.20482
2001	122.23307
2002	116.40775
2003	106.46732
2004	92.66407
2005	71.45155
2006	54.88881
2007	46.23248
2008	39.92185
2009	42.85292
2010	36.83289
2011	32.75558
2012	34.92072
2013	50.00719
2014	29.32378
2015	24.22825
2016	24.34427