Year	Percent
1970	6.36254
1971	5.59059
1972	2.92897
1973	2.62853
1974	2.80665
1975	4.69999
1976	5.11586
1977	8.79061
1978	12.53513
1979	17.63324
1980	17.97761
1981	18.48715
1982	22.61765
1983	28.66303
1984	35.72513
1985	40.21707
1986	48.29737
1987	69.7683
1988	75.57492
1989	81.07695
1990	81.17861
1991	83.33409
1992	95.99808
1993	114.73177
1994	123.39505
1995	117.60461
1996	132.23124
1997	111.30385
1998	126.69328
1999	144.80039
2000	127.24726
2001	126.49739
2002	151.80451
2003	175.84987
2004	152.92793
2005	117.12805
2006	108.5042
2007	104.41043
2008	86.49625
2009	35.24695
2010	30.81849
2011	25.84994
2012	27.09074
2013	25.19674
2014	22.30853
2015	20.25762
2016	21.18426