Year	gross (GPI)
1971	0.599370002746582
1972	0.665239989757538
1973	0.745890021324158
1974	0.819809973239899
1975	0.855549991130829
1976	0.880089998245239
1977	0.908259987831116
1978	0.918510019779205
1979	0.918309986591339
1980	0.920799970626831
1981	0.933860003948212
1983	0.93300998210907
1986	0.94242000579834
1999	0.985870003700256
2001	1.01745998859406
2002	1.00109994411469
2003	0.969500005245209
2004	0.971310019493103
2005	0.987909972667694
2006	0.957660019397736