Year	% of total
1971	84.84273617068074
1972	85.1107910760757
1973	85.14353718365959
1974	81.66898470097358
1975	81.27341639801342
1976	81.19596093636609
1977	81.00363323827011
1978	81.86154849529488
1979	80.52644929657164
1980	84.75007596475236
1981	83.33613304216362
1982	90.27759986824529
1983	90.50149158885104
1984	88.22728526127119
1985	85.48201166531891
1986	78.56812856812857
1987	70.64119879091903
1988	70.58942394379332
1989	71.8551841672936
1990	76.44007644007644
1991	76.56141165544462
1992	75.34077247405048
1993	74.5473454495857
1994	73.22269605576392
1995	74.0652084193149
1996	73.55655484699874
1997	74.35570020399582
1998	73.58411735578113
1999	72.14732149815303
2000	75.39054463661175
2001	74.00517283185603
2002	68.77162971248109
2003	64.12528979907263
2004	63.04451605203485
2005	63.79392415569198
2006	62.46563224711311
2007	64.59026480105739
2008	62.2510354763191
2009	59.57100156801255
2010	58.30246624156039
2011	57.06992716880244
2012	53.71855064773264
2013	50.82201655659938
2014	51.155165930243484
2015	53.06115038249249