| YEAR | PROD |
| 1960 | 2.9070 |
| 1961 | 2.9840 |
| 1962 | 3.0480 |
| 1963 | 3.1540 |
| 1964 | 3.2010 |
| 1965 | 3.2900 |
| 1966 | 3.4970 |
| 1967 | 3.7300 |
| 1968 | 3.8690 |
| 1969 | 3.9530 |
| 1970 | 4.1230 |
| 1971 | 4.0730 |
| 1972 | 4.0830 |
| 1973 | 3.9970 |
| 1974 | 3.8270 |
| 1975 | 3.6540 |
| 1976 | 3.5530 |
| 1977 | 3.6010 |
| 1978 | 3.7500 |
| 1979 | 3.6990 |
| 1980 | 3.7120 |
| 1981 | 3.7160 |
| 1982 | 3.7230 |
| 1983 | 3.7390 |
| 1984 | 3.8360 |
| 1985 | 3.8620 |
| 1986 | 3.7340 |
| 1987 | 3.6300 |
| 1988 | 3.5640 |
| 1989 | 3.3430 |
| 1990 | 3.2540 |
| 1991 | 3.3120 |
| 1992 | 3.2380 |
| 1993 | 3.1340 |
| 1994 | 3.0620 |
| 1995 | 3.0370 |
| 1996 | 3.0280 |
| 1997 | 3.0190 |
| 1998 | 2.9180 |
| 1999 | 2.8140 |
| 2000 | 2.7230 |
| 2001 | 2.6250 |
| 2002 | 2.5200 |
| 2003 | 2.4150 |
| 2004 | 2.3250 |
| 2005 | 2.2250 |
| 2006 | 2.1130 |
| 2007 | 2.0130 |
| 2008 | 1.8900 |
| 2009 | 1.7930 |
| 2010 | 1.7000 |
| 2011 | 1.5960 |
| 2012 | 1.5020 |
| 2013 | 1.4250 |
| 2014 | 1.3260 |
| 2015 | 1.2520 |
| 2016 | 1.1840 |
| 2017 | 1.1220 |
| 2018 | 1.0590 |
| 2019 | 1.0010 |
| 2020 | 0.9500 |
| 2021 | 0.8960 |
| 2022 | 0.8480 |
| 2023 | 0.7980 |
| 2024 | 0.7500 |
| 2025 | 0.7050 |
| 2026 | 0.6580 |
| 2027 | 0.6140 |
| 2028 | 0.5750 |
| 2029 | 0.5420 |
| 2030 | 0.5110 |
| 2031 | 0.4820 |
| 2032 | 0.4560 |
| 2033 | 0.4320 |
| 2034 | 0.4080 |
| 2035 | 0.3880 |
| 2036 | 0.3680 |
| 2037 | 0.3500 |
| 2038 | 0.3340 |
| 2039 | 0.3200 |