The Roman Empire experienced over 200 years of peace and prosperity known as Pax Romana after Augustus became the first emperor and established an effective system of government with civil servants rather than senators. The empire contained over 70 million residents and Rome itself had a population of 1 million. Agriculture was the most important industry and a common currency facilitated trade across the vast empire. This period of stability and growth ended after the death of Marcus Aurelius in 180AD.