By the time of the Persian Wars, when the great sea battles, Lade in 494 B.C., Salamis and Mycale in 480 and 479, brought sea power into the political reckoning of Greeks and Persians, the Greeks had worked out a far-ranging trade by sea. The Aegean region had become an important market centre. Rural towns of the eighth century had developed into city states, still largely agricultural, but increasingly dependent on the goods of trade for well-being and continued growth. Some cities, by the early fifth century, had substantial populations: Athens perhaps over 100,000 free men, women and children, and the Ionian cities, collectively, more than 250,000. In the cities there was a wealthy, if small, upper class, traditionally eager for luxuries, and a growing middle group, able to buy beyond their needs of subsistence. Some cities produced craft goods, olive oil and wine for export, as well as for local use, and all needed the constituents of bronze (copper and tin) and iron, scarce in the Aegean, for tools and weapons. Silver, mined in Attica and Thrace and found in small deposits in some Aegean islands, was in general demand for the new Aegean coinages, and electrum, available in Lydia, was used for jewellery and the coins issued by the Greek cities of western Asia Minor. Silver was needed, too, to pay for grain from Egypt and for the luxuries and exotics from the Levant. The slender threads of commerce, apparent in the eighth century in ventures from the Aegean to western Italy (Ischia) for metals and to the Levant (Al Mina) for eastern luxuries, had been woven into a complex net.