Year Total
1800 6.8
1801 6.8
1802 6.8
1803 6.8
1804 6.8
1805 6.8
1806 6.8
1807 6.8
1808 6.8
1809 6.8
1810 6.8
1811 6.8
1812 6.8
1813 6.8
1814 6.8
1815 6.8
1816 6.8
1817 6.8
1818 6.8
1819 6.8
1820 6.8
1821 6.8
1822 6.8
1823 6.8
1824 6.8
1825 6.8
1826 6.8
1827 6.8
1828 6.8
1829 6.8
1830 6.8
1831 6.8
1832 6.8
1833 6.8
1834 6.8
1835 6.8
1836 6.8
1837 6.8
1838 6.8
1839 6.8
1840 6.8
1841 6.8
1842 6.8
1843 6.8
1844 6.8
1845 6.8
1846 6.8
1847 6.8
1848 6.8
1849 6.8
1850 6.8
1851 6.8
1852 6.8
1853 6.8
1854 6.8
1855 6.8
1856 6.8
1857 6.8
1858 6.8
1859 6.8
1860 6.8
1861 6.8
1862 6.8
1863 6.8
1864 6.8
1865 6.8
1866 6.8
1867 6.8
1868 6.8
1869 6.8
1870 6.8
1871 6.8
1872 6.8
1873 6.8
1874 6.8
1875 6.8
1876 6.8
1877 6.8
1878 6.8
1879 6.8
1880 6.8
1881 6.8
1882 6.8
1883 6.8
1884 6.8
1885 6.8
1886 6.8
1887 6.8
1888 6.8
1889 6.8
1890 6.8
1891 6.8
1892 6.8
1893 6.8
1894 6.8
1895 6.8
1896 6.8
1897 6.8
1898 6.8
1899 6.8
1900 6.8
1901 6.52
1902 6.23
1903 6.22
1904 6.2
1905 6.19
1906 6.18
1907 6.16
1908 6.09
1909 6.01
1910 5.94
1911 5.86
1912 5.79
1913 5.72
1914 5.65
1915 5.58
1916 5.51
1917 5.44
1918 5.57
1919 5.69
1920 5.82
1921 5.94
1922 6.07
1923 6.04
1924 6.02
1925 5.99
1926 5.96
1927 5.94
1928 5.94
1929 5.95
1930 5.96
1931 5.97
1932 5.98
1933 5.95
1934 5.92
1935 5.89
1936 5.86
1937 5.83
1938 5.87
1939 5.9
1940 5.93
1941 5.96
1942 5.99
1943 6.07
1944 6.16
1945 6.24
1946 6.32
1947 6.41
1948 6.49
1949 6.58
1950 6.66
1951 6.68
1952 6.72
1953 6.74
1954 6.76
1955 6.78
1956 6.78
1957 6.78
1958 6.78
1959 6.77
1960 6.77
1961 6.76
1962 6.76
1963 6.75
1964 6.75
1965 6.76
1966 6.77
1967 6.79
1968 6.81
1969 6.83
1970 6.83
1971 6.79
1972 6.7
1973 6.56
1974 6.37
1975 6.13
1976 5.86
1977 5.59
1978 5.32
1979 5.06
1980 4.84
1981 4.64
1982 4.46
1983 4.3
1984 4.15
1985 4.02
1986 3.9
1987 3.79
1988 3.68
1989 3.57
1990 3.47
1991 3.37
1992 3.27
1993 3.18
1994 3.1
1995 3.02
1996 2.95
1997 2.88
1998 2.82
1999 2.77
2000 2.72
2001 2.67
2002 2.62
2003 2.58
2004 2.54
2005 2.5
2006 2.46
2007 2.42
2008 2.39
2009 2.36
2010 2.34
2011 2.32
2012 2.3
2013 2.27
2014 2.24
2015 2.22
2016 2.18
2017 2.15
2018 2.12