Year Total
1800 6
1801 6
1802 6
1803 6
1804 6
1805 6
1806 6
1807 6
1808 6
1809 6
1810 6
1811 6
1812 6
1813 6
1814 6
1815 6
1816 6
1817 6
1818 6
1819 6
1820 6
1821 6
1822 6
1823 6
1824 6
1825 6
1826 6
1827 6
1828 6
1829 6
1830 6
1831 6
1832 6
1833 6
1834 6
1835 6
1836 6
1837 6
1838 6
1839 6
1840 6
1841 6
1842 6
1843 6
1844 6
1845 6
1846 6
1847 6
1848 6
1849 6
1850 6
1851 6
1852 6
1853 6
1854 6
1855 6
1856 6
1857 6
1858 6
1859 6
1860 6
1861 6
1862 6
1863 6
1864 6
1865 6
1866 6
1867 6
1868 6
1869 6
1870 6
1871 6
1872 6
1873 6
1874 6
1875 6
1876 6
1877 6
1878 6
1879 6
1880 6
1881 6
1882 6
1883 6
1884 6
1885 6
1886 6
1887 6
1888 6
1889 6
1890 6
1891 6
1892 6
1893 6
1894 6
1895 6
1896 6
1897 6
1898 6
1899 6
1900 6
1901 6
1902 5.99
1903 5.99
1904 5.98
1905 5.98
1906 5.97
1907 5.97
1908 5.96
1909 5.96
1910 5.96
1911 5.95
1912 5.95
1913 5.94
1914 5.94
1915 5.93
1916 5.93
1917 5.92
1918 5.92
1919 5.93
1920 5.94
1921 5.95
1922 5.96
1923 5.97
1924 5.95
1925 5.93
1926 5.91
1927 5.89
1928 5.87
1929 5.9
1930 5.93
1931 5.96
1932 6
1933 6.03
1934 6.08
1935 6.13
1936 6.18
1937 6.23
1938 6.29
1939 6.3
1940 6.31
1941 6.32
1942 6.34
1943 6.36
1944 6.3
1945 6.25
1946 6.19
1947 6.14
1948 6.09
1949 5.28
1950 4.46
1951 4.76
1952 5.25
1953 5.64
1954 5.94
1955 6.16
1956 6.28
1957 6.33
1958 6.31
1959 6.23
1960 6.1
1961 5.93
1962 5.74
1963 5.53
1964 5.33
1965 5.13
1966 4.94
1967 4.77
1968 4.62
1969 4.47
1970 4.34
1971 4.19
1972 4.04
1973 3.86
1974 3.67
1975 3.46
1976 3.25
1977 3.05
1978 2.87
1979 2.7
1980 2.54
1981 2.4
1982 2.26
1983 2.11
1984 1.97
1985 1.84
1986 1.73
1987 1.65
1988 1.6
1989 1.58
1990 1.58
1991 1.6
1992 1.63
1993 1.64
1994 1.64
1995 1.62
1996 1.58
1997 1.53
1998 1.47
1999 1.41
2000 1.35
2001 1.29
2002 1.25
2003 1.21
2004 1.18
2005 1.17
2006 1.16
2007 1.16
2008 1.17
2009 1.18
2010 1.19
2011 1.21
2012 1.22
2013 1.24
2014 1.26
2015 1.28
2016 1.3
2017 1.31
2018 1.33