Year	% of total
1971	50.505050505050505
1972	35.28368794326241
1973	30
1974	28.173374613003094
1975	27.391304347826086
1976	24.699599465954606
1977	33.915211970074814
1978	36.99421965317919
1979	38.27800829875518
1980	29.98776009791922
1981	29.964328180737215
1982	29.966703662597116
1983	30.010718113612008
1984	30.010070493454176
1985	40.03254678600488
1986	34.82810164424514
1987	34.807831762146485
1988	35.268505079825836
1989	34.43223443223443
1990	36.76567656765676
1991	37.50752558699579
1992	33.35373317013464
1993	35.29062870699881
1994	39.66630785791173
1995	47.85407725321888
1996	47.93989335918565
1997	50.97674418604651
1998	46.94811800610376
1999	50.061906727197695
2000	53.950953678474114
2001	55.35211267605634
2002	58.38991270611057
2003	65.32498509242696
2004	68.07037784828381
2005	67.04129639309984
2006	69.6969696969697
2007	71.10137422824138
2008	73.42898656011624
2009	50.26960406716993
2010	17.295639418589147
2011	23.51271437019515
2012	29.853751589656635
2013	19.146246596654997
2014	21.65084388185654
2015	22.618226412202038