Year	gross (GPI)
1971	0.982720017433167
1972	0.984409987926483
1973	0.98022997379303
1974	0.976429998874664
1975	0.972630023956299
1976	0.963639974594116
1977	0.951569974422455
1978	0.953010022640228
1979	0.929750025272369
1980	0.955070018768311
1981	0.955839991569519
1982	1.00232994556427
1983	1.00243997573853
1984	1.00247001647949
1985	0.945479989051819
1986	0.946950018405914
1987	0.945640027523041
1988	0.885900020599365
1990	0.955560028553009
1991	0.951770007610321
1992	0.961070001125336
1993	0.956979990005493
1994	0.950070023536682
1995	0.954180002212524
1996	0.951319992542267
1998	0.955709993839264
1999	0.957040011882782
2000	0.957009971141815
2001	0.983169972896576
2002	0.961380004882813
2003	0.948889970779419
2004	0.949249982833862
2005	0.952470004558563
2006	0.950969994068146
2007	0.946370005607605
2008	0.945240020751953
2009	0.966069996356964
2010	0.970089972019196
2011	0.971270024776459
2012	0.971340000629425
2013	0.964850008487701
2014	0.958339989185333
2015	0.962520003318787
2016	0.964860022068024
2017	0.966840028762817
2018	0.974120020866394
2019	0.979139983654022
2020	0.988300025463104