Year	Percent
1970	26.31229
1971	33.90062
1972	32.40246
1973	35.88992
1974	35.8581
1975	39.02422
1976	40.58258
1977	42.38027
1978	50.52845
1979	54.96218
1980	77.08714
1981	102.91455
1982	127.53523
1983	144.03681
1984	134.58937
1985	153.42258
1986	135.21007
1987	147.63196
1988	143.42727
1989	177.01591
1990	187.32582
1991	199.24353
1992	189.11015
1993	197.03252
1994	230.72259
1995	188.74518
1996	173.9565
1997	141.86103
1998	123.55082
1999	112.59787
2000	124.13602
2001	117.2273
2002	108.31836
2003	89.68224
2004	89.21842
2005	73.03897
2006	79.7752
2007	73.58626
2008	55.5438
2009	63.76852
2010	48.77572
2011	52.39006
2012	36.41141
2013	32.9515
2014	28.37258
2015	35.70882
2016	32.3059