Source: Adapted from Our World Data.
Before the 20th century, the majority of famines and the related food shortages took place because of supply failures related to droughts and flooding. The lack of transportation and distribution capabilities prevented to compensate local shortages by bringing agricultural surpluses from other regions. The case of China is illustrative. While similar climatic conditions created a famine in the 1870s and the 1920s, the death toll was radically different. Between 9 to 13 million people were estimated to have died from the first famine while the figures went down to half a mi.lion for the second famine. The major explanation between these differences, in spite of population growth, was better distribution capabilities.
There are also contexts where a climatic event impact food supply and incite food traders to hoard supplies with the expectation that food prices will increase. This can remove a large quantity of food from the market, particularly if there are limited distribution capabilities. Monopolistic trading power was associated with famines in India (Punjab) and Bangladesh in the 1940s.
The political context behind famines is also highly relevant. Famine in a functioning democratic regime has never been observed, particularly since these regimes are associated with more effective market mechanisms. However, the worst famines in recorded history are associated with repressive communist and socialist regimes. Collectivization in the Soviet Union in the 1920s and political turmoil in China in the 1950s and 1960s (Great Leap Forward and Cultural Revolution) were associated with massive famines of 15 and 24 million deaths respectively.