Year	Percent
1970	38.08303
1971	51.09429
1972	54.79192
1973	46.36632
1974	37.025
1975	39.47771
1976	38.67221
1977	37.28563
1978	36.4596
1979	37.9939
1980	30.22385
1981	27.59885
1982	28.82294
1983	39.07761
1984	39.63967
1985	44.9114
1986	55.96162
1987	72.68446
1988	67.40384
1989	66.0586
1990	69.20978
1991	71.62074
1992	72.17554
1993	58.65227
1994	62.62531
1995	63.40285
1996	58.29302
1997	65.08904
1998	168.1778
1999	117.3583
2000	93.47986
2001	85.88766
2002	67.66334
2003	59.51741
2004	56.32658
2005	52.25813
2006	38.95263
2007	35.66671
2008	32.08853
2009	34.45301
2010	26.97575
2011	25.29483
2012	28.31466
2013	29.98622
2014	34.02891
2015	37.00133
2016	35.13192