Year	Percent
1961	2.46639
1962	6.09584
1963	7.84537
1964	6.25432
1965	9.16487
1966	8.17374
1967	8.53772
1968	5.91113
1969	5.13325
1970	8.769
1971	7.84602
1972	8.51792
1973	11.8496
1974	15.94511
1975	16.78178
1976	16.48992
1977	23.38307
1978	20.63104
1979	16.93163
1980	13.35483
1981	12.35119
1982	13.58232
1983	11.88425
1984	10.86473
1985	8.59548
1986	10.87882
1987	5.9442
1988	5.93613
1989	6.89619
1990	7.32625
1991	6.93514
1992	6.71077
1993	4.53724
1994	3.87984
1995	4.93313
1996	3.47072
1997	2.38183
1998	2.53276
1999	2.66484
2000	3.27607
2001	4.07987
2002	4.11499
2003	3.91891
2004	3.92128
2005	4.14949
2006	3.9782
2007	3.33114
2008	2.13544
2009	0.25253
2010	0.16042
2011	0.02897
2012	0.06795
2013	0.35361
2014	-0.19498
2015	0.61088
2016	0.2833
2017	0.95482