Following his deportation from the Soviet Union, Aleksandr Solzhenitsyn warned, "There always is this fallacious belief: 'It would not be the same here; here such things are impossible.'" Writing from his new home in Vermont, he went on: "the evil of the twentieth century is possible everywhere on earth." Near the conclusion of The Gulag Archipelago, his meticulously researched (and lived) account of the atrocities carried out under the name of socialism in the Soviet Union, he writes, "You may suddenly understand it someday — but only when you yourselves hear 'hands behind your backs there!' and step ashore on our Archipelago."

Solzhenitsyn directly experienced the abuse of power that is the natural consequence of centralizing political authority. As J.S. Mill wrote, "every increase of the functions devolving on the government is an increase of its power, both in the form of authority, and still more, in the indirect form of influence. The importance of this consideration, in respect to political freedom, has in general been quite sufficiently recognized…"

This insight was later developed by F.A. Hayek in The Road to Serfdom, where he claimed that individual and democratic liberty cannot be sustained under socialism, writing, "If 'capitalism' means here a competitive system based on free disposal over private property, it is far more important to realize that only within this system democracy is possible." But in some of my research, I find this somewhat of an unfair attribution, given that many of the prominent socialists Hayek was engaging also expressed concerns about the potential erosion of democratic freedoms under socialism. Karl Marx and Friedrich Engels were quite upfront in the Manifesto of the Communist Party about the "despotic inroads" that would be required "in the beginning" to "wrest, by degree, all capital from the bourgeoisie…"

But Hayek's hypothesis about the incompatibility of socialism and democratic freedom has been criticized in recent years, being called "wrong" by Nobel laureate Joseph Stiglitz (Columbia University) and an "idiotic claim" by Henry Farrell (Johns Hopkins University).

My recent research has sought to arbitrate these disputes. Using a new dataset put out by the Varieties of Democracy Project, my coauthors and I gathered all the data for every available country having both an annual measure of political liberty and a measure of their degree of socialism (state ownership of the economy — the economic definition of socialism). What we found was striking: not a single country, going all the way back to 1789, has sustained a high level of political freedom under socialism. In fact, only one country — Belarus in 1991 — maintained it for a single year. These results corroborate similar empirical tests by Robert Lawson and J.R. Clark on Milton Friedman's variant of the hypothesis, specifically the relationship between economic freedom and political freedom, and recent work on the deep relationship between democracy and capitalism by Vincent Geloso and Alex Tabarrok.