It is the degree to which governing institutions depend on revenues drawn from their citizens versus resources that rulers can control independently. Political scientist Margaret Levi famously argued (https://politicalscience.stanford.edu/publications/rule-and-revenue) that the history of governance is deeply intertwined with the history of revenue collection. How governments obtain revenue shapes incentives of rulers, leverage of citizens, and ultimately the distribution of both power and wealth. Across human history, societies have repeatedly developed mechanisms that constrained rulers, broadened participation, and moderated disparities in wealth. This article was produced by Human Bridges, a project of the Independent Media Institute.