Year	gross (GPI)
1971	0.422179996967316
1972	0.646690011024475
1973	0.767090022563934
1976	0.534500002861023
1978	0.477439999580383
1979	0.455680012702942
1980	0.454679995775223
1981	0.46110001206398
1982	0.462309986352921
1983	0.484259992837906
1984	0.501559972763062
1985	0.512189984321594
1987	0.540610015392303
1988	0.537810027599335
1989	0.551580011844635
1992	0.546630024909973
1993	0.550670027732849
1994	0.560930013656616
1995	0.574559986591339
1996	0.574119985103607
1997	0.573409974575043
1998	0.573729991912842
2000	0.666819989681244
2010	0.931110024452209