Year	gross (GPI)
1971	0.437579989433289
1972	0.625440001487732
1976	0.530520021915436
1978	0.460799992084503
1979	0.435930013656616
1980	0.435130000114441
1981	0.44310998916626
1982	0.437310010194778
1983	0.454879999160767
1984	0.464520007371902
1985	0.481460005044937
1987	0.523029983043671
1988	0.523689985275269
1989	0.5451700091362
2000	0.644640028476715