| Year | % change from year before in GRT | Year | % change from year before in GRT | Year | % change from year before in GRT |
| 1949 | __ | 1973 | 9 | 1997 | −0.2 |
| 1950 | 7 | 1974 | 6 | 1998 | 5 |
| 1951 | 30 | 1975 | 6 | 1999 | 6 |
| 1952 | 10 | 1976 | 5 | 2000 | 8.5 |
| 1953 | 18 | 1977 | 5 | 2001 | 11 |
| 1954 | 26 | 1978 | −1 | 2002 | −2 DWT |
| 1955 | 16 | 1979 | 1 | 2003 | 4 |
| 1956 | 26 | 1980 | 1 | 2004 | 5 |
| 1957 | 26 | 1981 | 1 | 2005 | 1 |
| 1958 | 15 | 1982 | −2 | 2006 | 4 |
| 1959 | 7 | 1983 | 6 | 2007 | 15 |
| 1960 | −1 | 1984 | −4.5 | 2008 | 20 |
| 1961 | 8 | 1985(*) | −−−− | 2009 | 1 |
| 1962 | 3 | 1986 | −3 | 2010 | −2 |
| 1963 | 13 | 1987 | 4 | 2011 | 1.5 |
| 1964 | 10 | 1988 | 1 | 2012 | 0.8 |
| 1965 | 12 | 1989 | −0.5 | 2013 | 0.4 |
| 1966 | 6 | 1990 | 3 | 2014 | 10 |
| 1967 | 11 | 1991 | 5 | 2015 | 8 |
| 1968 | 9 | 1992 | 7 | 2016 | 2 |
| 1969 | 13 | 1993 | 11 | 2017 | 2.5 |
| 1970 | 15 | 1994** | __ | 2018 | 4 |
| 1971 | 10 | 1995 | 8 | 2019 | −1.4 |
| 1972 | 15 | 1996 | 5 | 2020 | 0.44 |