A study on anti-Semitism in Germany offers the disturbing finding that “communities that murdered their Jewish populations during the 14th-century Black Death pogroms were more likely to demonstrate a violent hatred of Jews nearly 600 years later,” during the Nazi era. But cities

with more of an outward orientation—in particular, cities that were a part of the Hanseatic League of Northern Europe, which brought outside influence via commerce and trade—showed almost no correlation between medieval and modern pogroms. The same was true for cities with high rates of population growth—with sufficient in-migration, the newcomers may have changed the attitudes of the local culture.

Free trade helps lead to peace, prosperity, and the erosion of prejudice.