Year	% of total
1971	35.60035215400868
1972	35.29484536129623
1973	35.84296179300826
1974	37.46960005001989
1975	38.08993393217608
1976	36.522468530651665
1977	37.67670013329356
1978	37.77752443275002
1979	39.320180110248955
1980	40.316296558819936
1981	42.57308006797621
1982	44.10934931561067
1983	44.975118165397184
1984	44.763903150389694
1985	46.27605156376712
1986	46.602853603092186
1987	49.66510438540247
1988	50.60135007481518
1989	52.02363763524188
1990	52.68279885080916
1991	52.30527132748991
1992	53.549541328830344
1993	54.90888336978719
1994	55.002406084804804
1995	55.84915935572023
1996	57.013619191530886
1997	57.15228033737447
1998	56.93917327822028
1999	58.661694945786614
2000	58.57436278824195
2001	58.130132791267606
2002	57.645619761404454
2003	58.0219475300442
2004	59.82735442284047
2005	60.08080077750261
2006	60.92952138115297
2007	62.47639073163207
2008	61.6352139482148
2009	61.03428807402159
2010	60.27256849036288
2011	59.68738759696319
2012	59.48637100811253
2013	59.280142398261084
2014	61.58536145111177