Year	% of total
1971	80.60721062618596
1972	81.59472928456796
1973	82.29342327150084
1974	84.26492426492428
1975	85.11431411530815
1976	85.88052082882727
1977	89.2654304735397
1978	83.93843224373215
1979	81.08988764044945
1980	78.67289669432584
1981	79.76471758648992
1982	80.53429803812439
1983	67.29375639713409
1984	48.75483199524234
1985	34.41653593531815
1986	21.746615541122154
1987	6.998019039234029
1988	13.675203531841163
1989	15.924008751801056
1990	17.89581573677767
1991	24.000706370579667
1992	28.383331725667986
1993	24.3912329150208
1994	24.96229074454143
1995	23.340638956823213
1996	20.43434268650823
1997	18.46529259749498
1998	6.7371996908395
1999	5.970389989643287
2000	11.985401662241877
2001	11.542455286814583
2002	9.582358006573601
2003	9.214402475589395
2004	7.550216577744319
2005	6.263374188525139
2006	5.634772665125413
2007	5.9125861401016655
2008	3.4579308729186184
2009	4.386108626537607
2010	3.812022113150721
2011	3.19794328654964
2012	3.9869287200881462
2013	3.981847623403255
2014	3.186679514752705
2015	2.2792074665074122