Year	Percent
1973	5.94771
1974	6.42167
1975	35.50531
1976	49.39057
1977	63.82919
1978	71.10639
1979	87.21156
1980	63.66676
1981	35.5321
1982	29.57633
1983	24.84207
1984	22.40163
1985	21.92716
1986	22.68398
1987	20.53456
1988	18.63858
1989	17.68579
1990	16.4729
1991	12.44817
1992	6.85087
1993	5.08069
1994	4.30492
1995	10.64378
1996	24.21491
1997	14.71156
1998	7.78032
1999	8.40827
2000	13.08162
2001	21.49382
2002	18.47885
2003	27.93158
2004	37.30229
2005	40.10987
2006	82.11277
2007	137.58346
2008	139.80962
2009	148.62306
2010	52.1326
2011	34.58975
2012	27.04091
2013	13.19132
2014	11.40312
2015	8.58091
2016	8.53254