Did Karl Marx party in 1891? The effect of SPD 's Erfurt program on Karl Marx's citations

The Sozialdemokratische Partei Deutschlands (SPD) is often proposed as a pre‐Soviet popularizer of Marxist economic theories due to its electoral successes in Germany in the decades before World War I. Using the synthetic control method, we examine whether German‐language print references to Karl Marx responded to the SPD's adoption of the Marx‐inspired Erfurt Program of 1891. In doing so, we account for the near‐simultaneous repeal of anti‐socialist censorship laws in Germany. Evidence of a boost to Marx's citations from the Erfurt Program is modest, and cannot be distinguished from the effect of the censorship repeal on all socialist writers. These results suggest that the SPD's role in popularizing Marx was minor compared to later events such as the Russian Revolution of 1917.