Here’s a snippet from the paper “From Ancien RÃ©gime to Capitalism: The French Revolution as a Natural Experiment“, by Daron Acemoglu, Davide Cantoni, Simon Johnson & James Robinson:
In investigating the relationship between the collapse of the ancien rÃ©gime and the rise of capitalism it is therefore important to recognize both the possibility of reverse causality and omitted variable bias. In the natural sciences the solution to a problem like this would be to conduct an experiment. For instance, we would ideally take a group of countries which were alike and randomly assign ancien rÃ©gime institutions to some of them (the treatment group) while leaving unchanged the institutions of the rest (the Â‘controlÂ’ group). Then we could observe what happens to the relative prosperity of these two groups. In reality, we cannot conduct such an experiment. Nevertheless, social scientists can take advantage of natural experiments which history sometimes offers. In the context of the decline of the ancien rÃ©gime, the invasion of large parts of Europe by French armies following the French Revolution of 1789 provides a source of variation in institutions that can be used as a natural experiment. In this paper we argue that we can exploit this natural experiment as a way of estimating the effect of ancien rÃ©gime institutions on economic growth.
Their answer? The ancien rÃ©gime impeded economic growth.