Year	% of total
1971	86.08305159850323
1972	87.17309939494403
1973	85.9611750288023
1974	86.75491667634842
1975	87.19378506107881
1976	87.80389329917949
1977	87.65750955297452
1978	88.07443510670704
1979	88.63225726778316
1980	89.15601200242148
1981	90.44155570089224
1982	90.92021420706409
1983	92.15832515666662
1984	92.8405100893855
1985	93.41783463428432
1986	93.26304901928494
1987	93.74022970920537
1988	93.69366552654704
1989	93.89853856980794
1990	94.07344272790658
1991	93.88800277765374
1992	94.04718146498232
1993	93.96157784193645
1994	93.38439841785424
1995	93.81627816649494
1996	94.0772508291852
1997	94.15809928299302
1998	94.44745481117222
1999	94.01790376591819
2000	93.88155107079835
2001	94.22360414964939
2002	94.87049142610581
2003	94.97358000179425
2004	96.81736276374798
2005	96.23115195341178
2006	96.28099188185074
2007	96.04047938318936
2008	96.16210914490213
2009	96.40166313825308
2010	97.21176113497252
2011	96.79238920199651
2012	96.81680023221242
2013	98.46009118780151
2014	97.92892978784353