Year	Percent
1971	16.22299
1972	22.47396
1973	40.25092
1974	50.09806
1975	35.06871
1976	28.79554
1977	20.20604
1978	19.54091
1979	23.49959
1980	22.83938
1981	13.7516
1982	7.12882
1983	3.54046
1984	3.46684
1985	4.12279
1986	9.25831
1987	7.76281
1988	7.49653
1989	8.36988
1990	6.65874
1991	13.65254
1992	16.06215
1993	16.41833
1994	17.75205
1995	19.75909
1996	26.76203
1997	17.24653
1998	20.21608
1999	25.76744
2000	25.78708
2001	26.85438
2002	27.17257
2003	27.21944
2004	26.54914
2005	31.47664
2006	39.8681
2007	57.01712
2008	64.35173
2009	78.96164
2010	95.36136
2011	113.62657
2012	120.78211
2013	125.64927
2014	101.363
2015	100.02202
2016	104.32884