1919   15.3130                         
1920   15.9980                         
1921   15.1980                         
1922   16.1610                         
1923   16.7060                         
1924   16.6380                         
1925   16.7410                         
1926   17.0840                         
1927   16.8850                         
1928   16.5030                         
1929   16.3710                         
1930   15.0700                         
1931   13.6580                         
1932   11.6970                         
1933   11.0510