Year	% of tax revenue
1972	16.225165562913908
1973	15.484710474951205
1974	11.536471805483703
1975	10.461538461538462
1976	11.375
1977	11.444241316270567
1978	11.63586584531143
1979	11.618991447950457
1980	9.940855323020928
1981	7.904919845218353
1982	7.591785936527691
1983	7.226890756302522
1984	7.0818070818070815
1985	6.109375
1986	6.105990783410138
1987	5.925801577975491
1988	5.053863545684266
1989	4.002911208151383
1990	3.481568168519602
1991	3.631331767863133
1992	3.1956124314442413
1993	2.8146940822467403
1994	2.112412428472111
1995	1.982064608172832
1996	2.098679638637943
1997	1.968019680196802
1998	2.2353584024638615
1999	2.399661224297746
2000	2.4668779972364465
2001	2.595244183073383
2002	3.334126040428062
2003	0.08029093657016012
2004	0.10636883393165802
2005	0.09745401388719697
2006	0.09305654974946313
2007	0.07150825205228684