Year	% of total
1971	96.19163213040638
1972	96.38480148661132
1973	96.08888931276951
1974	95.40604822456702
1975	96.34799050540478
1976	96.14054756025331
1977	96.57340537652922
1978	96.70324385740469
1979	93.89619784177694
1980	90.7286529427183
1981	89.64703823156182
1982	88.5519531669638
1983	87.83674919113056
1984	87.16134910180841
1985	84.89539154204112
1986	82.48738750668065
1987	82.50397438313716
1988	82.38912190811973
1989	81.6322037914307
1990	81.62379661088792
1991	80.7167149576298
1992	80.83385367254475
1993	78.56660560960296
1994	76.22312499752614
1995	78.58278382500104
1996	78.20464218896358
1997	78.18582716322246
1998	78.480923314832
1999	75.94364347718454
2000	72.5158524953125
2001	73.07818429348129
2002	72.44125421080821
2003	72.18103991443351
2004	72.21614511819296
2005	72.10993160450248
2006	70.89196269022231
2007	70.92913786803447
2008	70.33797350395328
2009	70.02843872425709
2010	70.23777338678214
2011	68.51136316806758
2012	66.83286848686713
2013	66.42439973813104
2014	63.94609542736382
2015	64.09149509888022