A great review of this subject comes from a really interesting article by Danielle Allen published by The Washington Post. Take a look at this extract:
First, that’s because you have to count the people. While many ancient societies counted people for taxation, we get the word “census” from the ancient Romans. Part of their government was based on a popular sovereignty principle. In addition to using the numbers for purposes of taxation, they also used the census to organize voters. The moderncensus appeared with the American invention of constitutional democracy and the constitutional requirement for a decennial census. It is now a fixture of modern political and policy administration. Over time, the census became the basis for much of the work in social statistics that provides the foundation for modern policymaking.
Democracy is also about math because you use math for decision-making. Which decisions will be decided by a simple majority vote — by 50 percent plus one? Which will require a supermajority? And should that supermajority be a two-thirds or a three-quarters threshold?
The general idea is that you use a simple majority for matters of ordinary, passing and contingent concern. Supermajorities should be reserved for matters that rise to a constitutional level. (Here this, O ye Senate: Your filibuster does not accord with centuries of best practice in democratic design.)
Get full article here