Year	% of total primary
1971	10.8304300308228
1972	10.7629499435425
1973	10.8476400375366
1974	11.0814399719238
1975	11.6681900024414
2009	23.9187297821045
2010	22.5767803192139
2011	24.5248908996582
2012	23.9722900390625
2013	23.3386707305908
2014	23.7691097259521
2015	23.968090057373
2016	25.791919708252
2018	23.9752807617188