The graph of annual growth rates (at the top of the page) does not appear exactly as one would expect for long-term exponential growth. For exponential growth it should be a straight line at constant height, whereas in fact the graph from 1800 to 2005 is dominated by an enormous hump that began about 1920, peaked in the mid-1960s, and has been steadily eroding away for the last 40 years. The sharp fluctuation between 1959 and 1960 was due to the combined effects of the Great Leap Forward and a natural disaster in China.[9] Also visible on this graph are the effects of the Great Depression, the two world wars, and possibly also the 1918 flu pandemic.