Do you know the population growth rate of your city? The education levels of everyone on your block? Then you're a fan of demography, the branch of sociology that studies human behavior by analyzing statistical information.
The word demography comes from two ancient Greek words, demos, meaning "the people," and graphy, meaning "writing about or recording something" — so literally demography means "writing about the people." Like many branches of the sciences, demography began in the 19th century, when the general craze for cataloging information about the world really took off (think Darwin.) A common related word is demographics, referring to the raw statistical data that's used for analysis.