Year Years
1800 31.9
1801 31.9
1802 31.9
1803 31.9
1804 31.9
1805 31.9
1806 31.9
1807 31.9
1808 31.9
1809 31.9
1810 31.9
1811 31.9
1812 31.9
1813 31.9
1814 31.9
1815 31.9
1816 31.9
1817 31.9
1818 31.9
1819 31.9
1820 31.9
1821 31.9
1822 31.9
1823 31.9
1824 31.9
1825 31.9
1826 31.9
1827 31.9
1828 31.9
1829 31.9
1830 31.9
1831 31.9
1832 31.9
1833 31.9
1834 31.9
1835 31.9
1836 31.9
1837 31.9
1838 31.9
1839 31.9
1840 31.9
1841 31.9
1842 31.9
1843 31.9
1844 31.9
1845 31.9
1846 31.9
1847 31.9
1848 31.9
1849 31.9
1850 31.9
1851 31.9
1852 31.9
1853 31.9
1854 31.9
1855 31.9
1856 31.9
1857 31.9
1858 31.9
1859 31.9
1860 31.9
1861 31.9
1862 31.9
1863 31.9
1864 31.9
1865 31.9
1866 31.9
1867 31.9
1868 31.9
1869 31.9
1870 31.9
1871 31.87
1872 31.84
1873 31.82
1874 31.79
1875 31.76
1876 31.73
1877 31.7
1878 31.67
1879 31.65
1880 31.62
1881 31.59
1882 31.56
1883 31.53
1884 31.5
1885 31.48
1886 31.45
1887 31.42
1888 31.39
1889 31.36
1890 31.33
1891 31.31
1892 31.28
1893 31.25
1894 31.22
1895 31.19
1896 31.16
1897 31.14
1898 31.11
1899 31.08
1900 31.05
1901 31.02
1902 30.99
1903 30.97
1904 30.94
1905 30.91
1906 30.88
1907 30.85
1908 30.82
1909 30.8
1910 30.77
1911 30.74
1912 30.71
1913 30.68
1914 30.65
1915 30.63
1916 30.6
1917 30.57
1918 19.57
1919 30.51
1920 30.49
1921 30.46
1922 30.43
1923 30.4
1924 30.37
1925 30.34
1926 30.32
1927 30.29
1928 30.26
1929 30.23
1930 30.2
1931 30.17
1932 30.15
1933 30.12
1934 30.09
1935 30.06
1936 30.03
1937 30
1938 29.98
1939 29.95
1940 29.54
1941 29.23
1942 28.93
1943 28.15
1944 27.19
1945 25.2
1946 31.71
1947 33.54
1948 35.84
1949 36.72
1950 37.47
1951 37.56
1952 37.8
1953 38.04
1954 38.28
1955 38.52
1956 38.76
1957 39.01
1958 39.26
1959 39.49
1960 39.74
1961 39.99
1962 40.23
1963 40.47
1964 40.71
1965 40.95
1966 41.19
1967 41.43
1968 41.67
1969 41.91
1970 42.16
1971 42.6
1972 43.06
1973 43.54
1974 45.18
1975 45.67
1976 46.19
1977 46.58
1978 46.98
1979 47.4
1980 47.86
1981 48.43
1982 49
1983 49.59
1984 50.21
1985 50.7
1986 51.07
1987 51.43
1988 51.72
1989 52.16
1990 52.46
1991 52.96
1992 53.34
1993 53.66
1994 53.97
1995 54.52
1996 55.01
1997 55.52
1998 55.97
1999 56.54
2000 57.06
2001 57.55
2002 58.36
2003 59.02
2004 59.69
2005 60.28
2006 60.92
2007 61.67
2008 62.34
2009 63.06
2010 63.8
2011 64.56
2012 65.17
2013 65.71
2014 66.28
2015 66.78
2016 67.26
2017 67.6
2018 67.93