Year	% of total
1971	5.256014805675509
1972	10.32136501622527
1973	17.067725130240635
1974	20.571224562656194
1975	21.477707006369425
1976	20.588065391947318
1977	24.457437842393595
1978	17.206630725046608
1979	25.222511296727372
1980	24.80786416443253
1981	25.218822773628848
1982	35.76833126977576
1983	22.248477687903296
1984	25.176258403016888
1985	19.2835288118307
1986	20.213610449592263
1987	38.65618979587419
1988	39.4390756302521
1989	44.45856730915161
1990	52.4516936821089
1991	51.46118579047501
1992	52.12883685712622
1993	55.52070757440555
1994	61.009062263367454
1995	58.65664089620033
1996	60.112031870756155
1997	64.59673707359485
1998	74.00448465166627
1999	74.44065629661198
2000	75.66841615239477
2001	74.4597822997565
2002	75.34350495583001
2003	77.95981231885
2004	77.12349776536982
2005	74.83266699609182
2006	70.28575580490134
2007	70.95339876266019
2008	78.02032349787909
2009	76.0428242309256
2010	75.92366038659164
2011	66.80177628180562
2012	66.85805974610265
2013	59.85657346228004
2014	71.31849283890914
2015	79.26651534210161