Year	% of internal resources
1980	15.482
1981	15.873900000000003
1982	16.2658
1983	16.6577
1984	17.0496
1985	17.4415
1986	17.7213
1987	18.0011
1988	18.2809
1989	18.5607
1990	18.8405
1991	19.225
1992	19.6095
1993	18.7207
1994	17.8319
1995	16.9431
1996	16.0543
1997	15.165499999999998
1998	15.56016666665
1999	15.954833333350003
2000	16.3495
2001	16.26325
2002	16.177
2003	16.35933333335
2004	16.54166666665
2005	16.724
2006	16.11
2007	15.496000000000002
2008	14.330000000000002
2009	14.235150000000003
2010	14.289
2011	15.073
2012	14.0315
2013	13.578499999999998
2014	13.6485
2015	14.058000000000002
2016	13.218
2017	13.473000000000003
2018	13.461462155000001
2019	13.136039824999997
2020	13.136039824999997