Year	Percent
1970	46.35305
1971	42.75985
1972	40.57059
1973	38.16354
1974	40.36185
1975	38.63024
1976	50.92867
1977	65.66967
1978	82.77272
1979	62.79365
1980	55.35015
1981	42.37876
1982	52.3671
1983	70.98219
1984	75.05264
1985	83.78896
1986	106.38036
1987	90.95552
1988	132.00048
1989	90.18205
1990	82.25215
1991	62.46919
1992	58.8076
1993	70.6233
1994	61.94136
1995	60.81269
1996	54.41589
1997	52.77204
1998	56.32244
1999	59.82953
2000	57.28494
2001	54.43372
2002	53.31057
2003	53.30939
2004	50.31884
2005	41.57764
2006	36.13147
2007	34.36551
2008	31.06166
2009	33.25379
2010	30.92348
2011	28.41594
2012	30.26827
2013	29.80418
2014	31.95766
2015	36.3203
2016	37.73929