Year	Percent
1970	7.10781
1971	7.36064
1972	10.98924
1973	13.32229
1974	16.06411
1975	20.01932
1976	30.70562
1977	30.38273
1978	29.37578
1979	30.32178
1980	33.83031
1981	41.75691
1982	38.40278
1983	49.90633
1984	69.22486
1985	90.46463
1986	90.02086
1987	124.82931
1988	105.55578
1989	110.49383
1990	119.57142
1991	130.10788
1992	146.68398
1993	111.9608
1994	240.15985
1995	271.42979
1996	237.66538
1997	217.02505
1998	226.66896
1999	284.16834
2000	63.18458
2001	164.59325
2002	119.36396
2003	131.38382
2004	115.4752
2005	93.34641
2006	81.9921
2007	79.27421
2008	68.84182
2009	74.96886
2010	31.33401
2011	24.42126
2012	21.74185
2013	22.70614
2014	17.82299
2015	16.1334
2016	15.81633