Year	Percent
1970	33.03354
1971	34.48318
1972	36.43134
1973	34.99181
1974	40.25411
1975	46.13752
1976	46.01528
1977	47.29566
1978	52.34656
1979	57.47321
1980	62.04344
1981	146.4962
1982	170.9984
1983	118.16306
1984	95.77807
1985	100.02832
1986	90.11859
1987	87.15541
1988	80.89259
1989	72.49558
1990	53.78217
1991	58.70701
1992	48.21464
1993	42.28388
1994	38.54537
1995	34.17521
1996	30.85809
1997	28.49304
1998	30.12563
1999	34.06409
2000	32.95895
2001	32.22359
2002	32.24044
2003	34.47738
2004	32.22638
2005	33.8614
2006	31.94748
2007	32.29817
2008	29.44426
2009	26.26265
2010	22.61344
2011	25.16123
2012	31.80609
2013	35.77956
2014	40.61226
2015	44.99202
2016	46.94872