Darius I stimulated the Persian empire's economy by introducing reforms like standardized currency, road networks, and new agricultural techniques. He established imperial administrative systems including taxation codes, bureaucracies, and postal and judicial systems. This increased long-distance trade and economic growth. Similarly, ancient Greek city-states and the Roman Republic focused on agriculture and trade, with economies based around exporting staple crops. Standardized currencies and banking systems arose to facilitate regional and international commerce. Both the Persian and Roman empires eventually declined due in part to falling trade and taxation policies that overburdened peasants.