Year	Percent
1971	15.62051
1972	20.23072
1973	16.58574
1974	8.29353
1975	14.82828
1976	18.25958
1977	15.69576
1978	12.3467
1979	3.88239
1980	0.43446
1981	4.24263
1982	8.95743
1983	10.55417
1984	6.32138
1985	2.20323
1986	2.05253
1987	2.82083
1988	2.54024
1989	0.64203
1990	1.68799
1991	2.10158
1992	3.19922
1993	4.79411
1994	9.45875
1995	12.71486
1996	14.24089
1997	16.21039
1998	18.40191
1999	21.56952
2000	22.8574
2001	26.09604
2002	23.23517
2003	23.59524
2004	27.30829
2005	30.13084
2006	139.22078
2007	154.85123
2008	100.33506
2009	108.37016
2010	90.97039
2011	80.22637
2012	83.8012
2013	38.19063
2014	37.04476
2015	29.30781