Year	% of total
1971	33.22857771332671
1972	34.60015546577354
1973	34.667791370007585
1974	34.92372288562615
1975	35.836813016040324
1976	38.47662224027358
1977	37.840491204860896
1978	39.93790091050303
1979	37.127873902084865
1980	34.42606437749026
1981	30.991182198965824
1982	28.32559158583289
1983	25.917949317517657
1984	26.21690704827745
1985	24.94553320925769
1986	30.383355363009496
1987	29.86659799861233
1988	28.364517518717896
1989	27.58919303576141
1990	23.70435049174729
1991	23.321474217216682
1992	27.598217965125237
1993	28.55316938985868
1994	28.245257080648763
1995	25.15002986045331
1996	32.018153131506736
1997	32.10809864626992
1998	30.82691938880978
1999	40.89197809321459
2000	37.13014925768803
2001	34.29839715323069
2002	37.848715628454634
2003	32.501440508150054
2004	24.930573299368447
2005	25.391256721861748
2006	21.449164275092762
2007	24.25328525021593
2008	24.61665795732753
2009	22.717803626141237
2010	23.231507425683148
2011	20.867761643715227
2012	24.680154081114317
2013	26.658121501487326
2014	26.492330023755162