Year	Percent
1970	4.72459
1971	4.23959
1972	4.44812
1973	3.99429
1974	7.22172
1975	7.90817
1976	35.79298
1977	43.74956
1978	40.15501
1979	43.40779
1980	35.42591
1981	47.89288
1982	64.03899
1983	77.28658
1984	98.06213
1985	118.44085
1986	103.47696
1987	104.037
1988	97.36022
1989	87.33908
1990	74.13159
1991	72.86421
1992	69.57535
1993	70.63179
1994	107.20662
1995	90.78202
1996	96.74083
1997	105.7374
1998	108.00058
1999	104.97309
2000	114.84391
2001	110.91149
2002	110.92819
2003	92.19334
2004	83.57852
2005	76.59125
2006	72.8799
2007	62.33723
2008	53.27811
2009	55.14551
2010	52.97476
2011	47.47088
2012	44.9206
2013	24.40804
2014	22.34073
2015	23.47139
2016	25.89304