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 6.81
1864 6.81
1865 6.81
1866 6.81
1867 6.81
1868 6.81
1869 6.81
1870 6.81
1871 6.81
1872 6.81
1873 6.81
1874 6.81
1875 6.81
1876 6.81
1877 6.81
1878 6.81
1879 6.81
1880 6.81
1881 6.81
1882 6.81
1883 6.81
1884 6.81
1885 6.81
1886 6.81
1887 6.81
1888 6.81
1889 6.81
1890 6.81
1891 6.81
1892 6.81
1893 6.81
1894 6.81
1895 6.81
1896 6.81
1897 6.81
1898 6.81
1899 6.81
1900 6.81
1901 6.81
1902 6.81
1903 6.81
1904 6.81
1905 6.81
1906 6.81
1907 6.81
1908 6.81
1909 6.81
1910 6.81
1911 6.81
1912 6.81
1913 6.81
1914 6.81
1915 6.81
1916 6.81
1917 6.81
1918 6.81
1919 6.81
1920 6.81
1921 6.81
1922 6.81
1923 6.81
1924 6.81
1925 6.81
1926 6.81
1927 6.81
1928 6.81
1929 6.81
1930 6.81
1931 6.81
1932 6.81
1933 6.81
1934 6.81
1935 6.81
1936 6.81
1937 6.81
1938 6.82
1939 6.82
1940 6.82
1941 6.82
1942 6.82
1943 6.82
1944 6.82
1945 6.82
1946 6.82
1947 6.82
1948 6.82
1949 6.82
1950 6.82
1951 6.81
1952 6.8
1953 6.79
1954 6.79
1955 6.8
1956 6.82
1957 6.85
1958 6.88
1959 6.91
1960 6.95
1961 7
1962 7.05
1963 7.09
1964 7.14
1965 7.18
1966 7.22
1967 7.25
1968 7.27
1969 7.28
1970 7.29
1971 7.3
1972 7.31
1973 7.33
1974 7.35
1975 7.37
1976 7.39
1977 7.41
1978 7.42
1979 7.42
1980 7.42
1981 7.42
1982 7.42
1983 7.44
1984 7.46
1985 7.49
1986 7.51
1987 7.53
1988 7.53
1989 7.53
1990 7.51
1991 7.47
1992 7.43
1993 7.39
1994 7.34
1995 7.29
1996 7.24
1997 7.18
1998 7.13
1999 7.07
2000 7.01
2001 6.95
2002 6.89
2003 6.82
2004 6.76
2005 6.69
2006 6.62
2007 6.53
2008 6.45
2009 6.35
2010 6.26
2011 6.16
2012 6.06
2013 5.96
2014 5.87
2015 5.78
2016 5.7
2017 5.62
2018 5.53