Year	% of internal resources
1980	13.684596577017114
1981	13.833751309804402
1982	13.982906042616136
1983	14.132060775403424
1984	14.281215508215158
1985	14.430370241002443
1986	14.57952497381418
1987	14.728679706601467
1988	14.877834439388755
1989	15.026989172200489
1990	15.176143904987773
1991	15.325298637799511
1992	15.474453370586797
1993	15.623608103398531
1994	15.77276283618582
1995	15.921917568973104
1996	16.071072301784838
1997	16.22022703457213
1998	16.369381767383864
1999	16.518536500171148
2000	16.667691232982886
2001	16.81684596577017
2002	17.67726161369193
2003	18.2640586797066
2004	18.38630806845966
2005	18.630806845965772
2006	18.82640586797066
2007	19.229828850855746
2008	19.50633251833741
2009	18.73838630806846
2010	19.469437652811735
2011	19.43276283618582
2012	20.227383863080686
2013	19.963325183374085
2014	20.765281173594133
2015	20.943765281173594
2016	21.167970660146697
2017	21.47677261613692
2018	21.721271393643033
2019	21.846210268948653
2020	21.89437652811736