Year	% of total
1971	55.97949886104784
1972	66.95042563845769
1973	56.540084388185655
1974	58.41885214747244
1975	60.10033444816053
1976	57.1764705882353
1977	63.77139166935745
1978	71.80688531269097
1979	76.81019190453152
1980	82.07144761396961
1981	81.07354478912512
1982	86.79530836171018
1983	82.67547481420314
1984	81.71340478637498
1985	72.8543055752589
1986	47.03439790844312
1987	48.1784548422198
1988	45.1966191817785
1989	39.56559388079088
1990	46.93421495699023
1991	47.04606320299946
1992	46.19998554669621
1993	46.02863436123348
1994	22.968184119319286
1995	16.353285016809423
1996	16.18333234894572
1997	21.630241065566082
1998	18.408980240395707
1999	17.74893790374207
2000	19.653897669434773
2001	19.383925573310684
2002	23.3429128510308
2003	24.95264397117921
2004	29.936835798040995
2005	30.815736028667988
2006	29.067722736563667
2007	26.464112106140654
2008	28.69091785757336
2009	22.538175973056756
2010	20.117227769432418
2011	22.995687422648935
2012	14.95725641153827
2013	12.38403851495232
2014	11.476416998718602
2015	8.39801012035011