Year	% of total
1971	63.10714285714286
1972	61.58620689655172
1973	65.33105996021598
1974	58.65110246433204
1975	69.77520587580682
1976	76.52223706814277
1977	47.76869893148963
1978	41.225271218889596
1979	41.785009861932934
1980	21.382763770535007
1981	10.893286480488255
1982	11.819379391100702
1983	5.517454433117084
1984	5.760830464052623
1985	7.700376674772326
1986	7.672634271099745
1987	8.44069302532208
1988	20.255863539445627
1989	22.694886839899414
1990	15.675
1991	15.88659298414224
1992	17.047430830039527
1993	18.422053231939163
1994	21.510714285714286
1995	20.250142890764213
1996	20.491994274491528
1997	19.100827317973565
1998	18.11278074002262
1999	19.142667046858662
2000	18.761755485893417
2001	16.259960931443988
2002	13.24159111714851
2003	10.458715596330276
2004	5.883263663105744
2005	32.89473684210527
2006	41.930047600745056
2007	38.92048018774258
2008	49.47950553025374
2009	48.09364018284144
2010	30.80682096998446
2011	33.402593547668964
2012	22.332565517840845
2013	21.149566943959467
2014	21.948412229961043
2015	24.41745741562926