Because democracy is central to much comparative and international political research, it is crucial for political scientists to measure it validly. We challenge the common assumption that most existing indicators of democracy measure the same single dimension. We present 11 different streams of evidence to show that about three-quarters of what Polity, Freedom House, and other indicators of democracy have been measuring consists of variation on the two dimensions of democracy that Robert Dahl proposed in Polyarchy-contestation and inclusiveness. These two dimensions were consistently fundamental to the most commonly used indicators of democracy from 1950 to 2000. Our analysis produces new indicators of contestations and inclusiveness for most countries from 1950 to 2000.