Year Total 1800 6.4 1801 6.4 1802 6.4 1803 6.4 1804 6.4 1805 6.4 1806 6.4 1807 6.4 1808 6.4 1809 6.4 1810 6.4 1811 6.4 1812 6.4 1813 6.4 1814 6.4 1815 6.4 1816 6.4 1817 6.4 1818 6.4 1819 6.4 1820 6.4 1821 6.4 1822 6.4 1823 6.4 1824 6.4 1825 6.4 1826 6.4 1827 6.4 1828 6.4 1829 6.4 1830 6.4 1831 6.4 1832 6.4 1833 6.4 1834 6.4 1835 6.4 1836 6.4 1837 6.4 1838 6.4 1839 6.4 1840 6.4 1841 6.4 1842 6.4 1843 6.4 1844 6.4 1845 6.4 1846 6.4 1847 6.4 1848 6.4 1849 6.4 1850 6.4 1851 6.4 1852 6.4 1853 6.4 1854 6.4 1855 6.4 1856 6.4 1857 6.4 1858 6.4 1859 6.4 1860 6.4 1861 6.4 1862 6.4 1863 6.4 1864 6.4 1865 6.4 1866 6.4 1867 6.4 1868 6.4 1869 6.4 1870 6.4 1871 6.4 1872 6.4 1873 6.4 1874 6.4 1875 6.4 1876 6.4 1877 6.4 1878 6.4 1879 6.4 1880 6.4 1881 6.4 1882 6.4 1883 6.4 1884 6.4 1885 6.4 1886 6.4 1887 6.4 1888 6.4 1889 6.4 1890 6.4 1891 6.4 1892 6.4 1893 6.4 1894 6.4 1895 6.4 1896 6.4 1897 6.4 1898 6.4 1899 6.4 1900 6.4 1901 6.4 1902 6.4 1903 6.4 1904 6.4 1905 6.4 1906 6.4 1907 6.4 1908 6.4 1909 6.4 1910 6.4 1911 6.4 1912 6.4 1913 6.4 1914 6.4 1915 6.4 1916 6.4 1917 6.4 1918 6.4 1919 6.4 1920 6.4 1921 6.4 1922 6.4 1923 6.4 1924 6.4 1925 6.4 1926 6.4 1927 6.4 1928 6.4 1929 6.4 1930 6.4 1931 6.38 1932 6.35 1933 6.32 1934 6.3 1935 6.27 1936 6.24 1937 6.22 1938 6.19 1939 6.16 1940 6.13 1941 6.11 1942 6.08 1943 6.05 1944 6.02 1945 5.99 1946 5.96 1947 5.44 1948 4.88 1949 5.77 1950 6.66 1951 6.66 1952 6.68 1953 6.7 1954 6.73 1955 6.77 1956 6.81 1957 6.85 1958 6.88 1959 6.92 1960 6.94 1961 6.97 1962 6.99 1963 7.01 1964 7.02 1965 7.01 1966 6.98 1967 6.94 1968 6.88 1969 6.8 1970 6.71 1971 6.59 1972 6.47 1973 6.33 1974 6.19 1975 6.04 1976 5.89 1977 5.73 1978 5.57 1979 5.41 1980 5.24 1981 5.08 1982 4.92 1983 4.75 1984 4.59 1985 4.43 1986 4.25 1987 4.07 1988 3.88 1989 3.68 1990 3.48 1991 3.28 1992 3.09 1993 2.91 1994 2.75 1995 2.61 1996 2.49 1997 2.38 1998 2.29 1999 2.21 2000 2.14 2001 2.09 2002 2.05 2003 2.02 2004 2 2005 1.99 2006 2 2007 2.02 2008 2.06 2009 2.1 2010 2.14 2011 2.18 2012 2.21 2013 2.23 2014 2.23 2015 2.22 2016 2.2 2017 2.18 2018 2.15