Year	% of total
1971	69.03039073806077
1972	71.55963302752293
1973	70.15834348355664
1974	67.13947990543736
1975	57.97546012269939
1976	58.51648351648352
1977	60.20151133501259
1978	59.211584875301696
1979	57.46268656716418
1980	53.5305985205111
1981	61.648745519713266
1982	59.72938144329897
1983	59.28358208955223
1984	53.492063492063494
1985	47.33364794714488
1986	46.41425389755011
1987	44.13793103448276
1988	42.00359389038634
1989	49.71932638331997
1990	48.143664245359155
1991	46.32050803137841
1992	50.66755674232309
1993	50.369276218611525
1994	44.90818030050083
1995	40.049321824907516
1996	41.85044359949303
1997	37.930258717660294
1998	22.928243537086253
1999	22.3755119637853
2000	36.96756545525596
2001	38.85689912561314
2002	41.65351223362273
2003	38.24884792626728
2004	42.931003743982885
2005	49.81715425531915
2006	53.942245295262815
2007	56.55571182997343
2008	61.476895197825435
2009	75.47386559448593
2010	67.6786424499536
2011	76.18565058775842
2012	72.36302646291465
2013	72.0421327672083
2014	62.36490781945327
2015	58.85410144020038