Year	% of total
1971	58.199191881169746
1972	57.77346614335619
1973	58.80490918037338
1974	60.22126061803499
1975	62.074832379098034
1976	62.26744024619242
1977	63.055485918385415
1978	61.76383529200221
1979	61.44138385357433
1980	64.13861059674959
1981	63.34010355463544
1982	62.54769169507631
1983	59.16433501177277
1984	59.311152329097496
1985	59.085674556081024
1986	61.555868150567015
1987	63.73177838349413
1988	65.2166844812849
1989	63.55264502106828
1990	63.28006274741853
1991	62.65214325592092
1992	64.20497477700856
1993	65.57455066088805
1994	66.36034230325956
1995	68.62247109223986
1996	69.50434709809676
1997	68.61724901267728
1998	69.76566571532771
1999	71.19740133971496
2000	69.90923824800348
2001	67.54891156994341
2002	67.40480062904062
2003	66.547291841545
2004	69.74942824154712
2005	71.55882900664236
2006	68.94929299614208
2007	70.35520249256389
2008	76.5710597584081
2009	73.407523374139
2010	68.26017767999227
2011	73.87026164838275
2012	76.65912385704866
2013	76.24394605889691
2014	79.55568357348682