Year	% of total primary
1971	0
1972	0
1973	0
1974	0
1975	0
1987	0.107569999992847
1988	0.317149996757507
1991	0.713389992713928
1992	0.730719983577728
1993	0.475699990987778
1994	0.57125997543335
1995	0.377449989318848
1999	1.87625002861023
2000	2.8011200428009
2001	3.17542004585266
2002	3.29815006256104
2003	4.44902992248535
2004	7.00998020172119
2005	7.98778009414673
2006	7.41400003433228
2007	9.24147033691406
2008	9.68653964996338
2009	9.0216703414917
2010	11.4098501205444
2011	11.1126203536987
2012	12.8443002700806
2013	14.2110204696655
2014	14.774359703064
2015	15.7623500823975
2016	14.0924596786499
2018	15.6583404541016
2019	15.9614295959473