In the US, there are two death investigation systems, the coroner system based on English law, and the medical examiner system, which evolved from the coroner system during the latter half of the 19th century. The type of system varies from municipality to municipality and from state to state, with over 2,000 separate jurisdictions for investigating unnatural deaths. In 2002, 22 states had a medical examiner system, 11 states had a coroner system, and 18 states had a mixed system. Since the 1940s, the medical examiner system has gradually replaced the coroner system, and serves about 48% of the US population.