Year	% of total primary
1970	9.00697994232178
1999	8.4639196395874
2000	8.33108997344971
2001	8.05601978302002
2002	8.72605991363525
2003	9.12038993835449
2004	9.93344020843506
2005	10.2803602218628
2007	10.6691598892212
2008	12.0762796401978
2009	12.812689781189
2010	13.7780704498291
2011	14.6898002624512
2012	15.8553104400635
2013	16.1735401153564
2014	16.8572692871094
2015	17.3389701843262
2016	17.8312091827393
2017	17.7723693847656
2018	18.2064399719238
2019	18.6570301055908
2020	18.6220607757568
2021	17.510929107666