Fig. 3: Average tariffs in the decades 1910s, 1920s and 1930s.
From: Pandemics and protectionism: evidence from the “Spanish” flu

The maps show standardized tariff intervals, in order to make the decades comparable to one another. Panel (A) shows the average tariffs for 1910–1919, Panel (B) shows the average tariffs for the interval 1920–1929, and Panel (C) shows the average tariffs for 1930–1939.