Year	% of total
1971	56.93384989981992
1972	57.87197962752229
1973	58.49990681359922
1974	58.622598076011045
1975	61.18477369484207
1976	61.83315722386661
1977	64.22112272781409
1978	66.42996788079078
1979	66.56045904904602
1980	66.10260957172798
1981	65.43811207574382
1982	65.78389961613453
1983	66.75674444511733
1984	67.94415293422558
1985	68.31926744829802
1986	69.06350644736239
1987	69.93846160923948
1988	70.85727551593584
1989	70.93823289897979
1990	71.96410226976447
1991	71.44935912128919
1992	72.06793178521485
1993	73.4236272672784
1994	73.95347028292423
1995	75.34927238980008
1996	76.0150402683546
1997	76.14940145904889
1998	75.94768766266769
1999	76.32184864075215
2000	76.68428394442934
2001	77.14802926720792
2002	78.21227920037893
2003	80.13212570239374
2004	81.79183146632417
2005	82.99371947884525
2006	83.91060117091186
2007	84.54844309444233
2008	84.39751332479851
2009	84.68017523268965
2010	85.52025359539562
2011	86.12799823326775
2012	85.69478094878316
2013	85.68097945681716
2014	85.49959454646074