Year	Percent
1970	15.95379
1971	16.7724
1972	14.3461
1973	17.67024
1974	22.6044
1975	27.39952
1976	39.3561
1977	56.83003
1978	102.02535
1979	126.81982
1980	102.34928
1981	108.57228
1982	121.53653
1983	126.89152
1984	118.03158
1985	128.85687
1986	104.54893
1987	102.83408
1988	91.83731
1989	89.53383
1990	80.12873
1991	85.96182
1992	81.19037
1993	107.06395
1994	156.19582
1995	116.61258
1996	103.34932
1997	91.47078
1998	94.10822
1999	100.05557
2000	114.28053
2001	109.20386
2002	110.24854
2003	104.94987
2004	96.57592
2005	81.1054
2006	83.00373
2007	79.01196
2008	58.75311
2009	61.71362
2010	46.28858
2011	19.45715
2012	22.75241
2013	26.05702
2014	24.45957
2015	28.4115
2016	29.05971