Year	% of total
1971	35.98250336473755
1972	34.44656488549619
1973	37.002412545235224
1974	38.841743119266056
1975	43.868852459016395
1976	42.28813559322034
1977	45.06680369989722
1978	45.10978043912176
1979	45.780795344325895
1980	47.985849056603776
1981	48.76492194674013
1982	48.68067978533095
1983	49.69049694856146
1984	46.4030612244898
1985	47.93625498007968
1986	43.4901185770751
1987	43.137931034482754
1988	41.820788530465954
1989	45.81506849315068
1990	40.05054151624549
1991	42.49809885931559
1992	42.05668016194332
1993	39.68778280542987
1994	40.12121212121212
1995	36.80434782608696
1996	36.46948356807512
1997	39.21243523316062
1998	33.92941176470588
1999	39.075268817204304
2000	43.31443298969072
2001	42.51485148514851
2002	41.171116504854375
2003	39.48471282979331
2004	38.579165339280024
2005	39.04067737430167
2006	40.90037887229775
2007	34.7581656832226
2008	36.005171299288946
2009	38.012969186349224
2010	35.51514032496307
2011	28.13897846665973
2012	26.94946974422957
2013	21.05607680558586
2014	24.133117426992015
2015	21.285579092960617