Year	% of total primary
1972	7.70662021636963
1973	7.59051990509033
1974	7.39408016204834
1975	7.08713006973267
1976	6.90951013565063
1977	6.8630199432373
1978	6.81720018386841
1979	6.80573987960815
1980	6.80725002288818
1981	6.83880996704102
1982	6.90120983123779
1983	7.00071001052856
1984	7.12146997451782
1985	7.15910005569458
1986	7.23601007461548
1987	7.29176998138428
1988	7.42175006866455
1989	7.58971977233887
1990	7.68381023406982
1991	7.72990989685059
1992	7.81603002548218
1993	7.92117977142334
1994	8.05084991455078
1995	8.070969581604
1996	8.1575403213501
1997	8.21286010742188
1998	8.28359985351562
1999	8.46527004241943
2000	8.57030963897705
2001	8.81027030944824
2002	8.84465980529785
2003	9.84805965423584
2004	10.3503503799438
2005	11.2405700683594
2006	12.0692195892334
2007	13.0158500671387
2008	13.7294797897339
2009	14.5024299621582
2010	15.2679996490479
2011	16.006290435791
2012	16.8204708099365
2013	17.5812702178955
2014	18.3533496856689
2015	18.6214904785156
2016	18.5134391784668
2017	19.0780792236328
2018	20.8428592681885
2019	20.887170791626
2020	21.3994693756104
2021	21.1276702880859
2022	21.6067905426025