Year	% of total
1971	83.41282458929517
1972	64.68484577559231
1973	70.78095238095237
1974	86.9698294709226
1975	69.08198614318707
1976	70.79883097905504
1977	61.29853596435392
1978	50.753439615636594
1979	52.64415418923224
1980	38.819919096108244
1981	30.735596707818928
1982	28.98499765588373
1983	22.827958223344428
1984	29.697239536954584
1985	30.241659328832792
1986	33.71725803455322
1987	29.152241455836663
1988	34.39162519306676
1989	32.31093420744556
1990	32.58560499145807
1991	41.864897296534195
1992	40.84535526493192
1993	38.414339882799034
1994	35.81224647479235
1995	34.6849971621366
1996	33.860740011081695
1997	34.70248805608984
1998	38.21719277347628
1999	38.21244328423146
2000	38.215522509676106
2001	38.21627215108007
2002	38.217683917382224
2003	36.90051525961157
2004	33.400617919670445
2005	33.00055227494796
2006	27.10082215491129
2007	27.099834624423362
2008	27.100900047370914
2009	22.900338777367647
2010	24.401822288580068
2011	21.761485536731524
2012	19.71364871455445
2013	18.439912751445487
2014	17.59131293188549
2015	18.195125055686372