Year	% of total
1971	0.2105314041966769
1972	0.20446672288519507
1973	0.24040458237479337
1974	0.32237841367050324
1975	0.35609627607182404
1976	0.41150944734715283
1977	0.396214062003695
1978	0.35556027447989974
1979	0.492288951434726
1980	0.6649779456528696
1981	0.8210240862291333
1982	0.9414770000306811
1983	1.0322825587957467
1984	1.0259156170037314
1985	1.009505123330925
1986	1.0730437994574344
1987	1.069266173228277
1988	1.0771743281317065
1989	1.0763064310742823
1990	1.0851018085772526
1991	1.1544477720357305
1992	1.1722887367415789
1993	1.122505124920851
1994	1.1417507292003954
1995	1.1520645827503668
1996	1.101487472312108
1997	1.0972716301864816
1998	1.1418640303129726
1999	1.240334902505431
2000	1.3845710770252748
2001	1.4208988755830654
2002	1.4171648345764092
2003	1.4451787947886046
2004	1.4988768947659035
2005	1.567383752837478
2006	1.6392685270457636
2007	1.7581439149520124
2008	1.846723296546536
2009	2.073918310109429
2010	2.1839929027410774
2011	2.3699027399089276
2012	2.661397639723697
2013	2.8879506799373686
2014	3.2070026288432167
2015	3.558132089199991