Year	% of total
1971	55.5049142874384
1972	56.488365617808974
1973	57.166554132851076
1974	57.26261722355117
1975	59.99253650471822
1976	60.62372592180456
1977	63.1285322882053
1978	65.41313936265774
1979	65.49117773407652
1980	64.94159215242897
1981	64.21436913735923
1982	64.5497924429521
1983	65.55989775455207
1984	66.82731690896117
1985	67.21185532782073
1986	68.05793490108819
1987	69.06212580483263
1988	70.05172243672095
1989	70.16228716006614
1990	71.32276919418221
1991	70.8229487065002
1992	71.57554889871717
1993	73.03492027775347
1994	73.64162124930014
1995	75.11197114011715
1996	75.8322690674773
1997	75.972247790891
1998	75.7866499553921
1999	76.15018793389422
2000	76.5031914828062
2001	76.9720460911869
2002	78.07126293703567
2003	80.02687866547838
2004	81.71376203283185
2005	82.9294235237653
2006	83.85605811825242
2007	84.52437505130128
2008	84.36508025160185
2009	84.7981046833971
2010	85.63468125915465
2011	86.22295973330327
2012	85.78078330668536
2013	85.75901448041863
2014	85.57760364411332