the Istrian–Dalmatian exodus were relocated in the Nurra region, along the north-western coastline. As a result of the city's originally diverse composition, Carbonia developed a variety of Italian with some Sardinian influences from the neighbouring areas, while the other mainland coloni ("colonists") establishing minor centres kept their dialects of Istriot, Venetian and Friulan, which are still spoken by the elderly. In the same period, a few Italian Tunisian families settled in the sparsely populated area of Castiadas, east of Cagliari. Following the Italian economic miracle, a historic migratory movement from the inland to the coastal and urban areas of Cagliari, Sassari-Alghero-Porto Torres and Olbia, where today most Sardinians live, took place. Demographics With a population density of 69/km2, slightly more than a third of the national average, Sardinia is the fourth least populated region in Italy. The population distribution is anomalous compared to that of other Italian regions lying on the sea. In fact, contrary to the general trend, urban settlement has not taken place primarily along the coast but towards the centre of the island. Historical reasons for this include the repeated Moorish raids during the Middle Ages, which made the coast unsafe, widespread pastoral activities inland, and the swampy nature of the coastal plains that were reclaimed only in the 20th century. Similarly to the Celtic clans, the Sardinians have in fact tended to retreat into the less accessible interior to keep their own independence and way of life. The situation has been recently reversed with the expansion of seaside tourism; today all Sardinia's major urban centres are located near the coast, while the island's interior is very sparsely populated. It is the region of Italy with the lowest total fertility rate (1.087 births per woman), and the region with the second-lowest birth rate. However, the population in Sardinia has increased in recent years because of immigration, mainly proceeding from continental Italy and Sicily, but also from Eastern Europe (esp. Romania), Africa and Asia. As of 2013, there were 42.159 foreign (that is, any people who have not applied for Italian citizenship) national residents, forming 2.5% of the total population. Life expectancy and longevity Average life expectancy is slightly over 82 years (85 for women and 79.7 for men). Sardinia is the first discovered Blue Zone, a demographic and/or geographic area of the world where people live measurably longer lives. Sardinians share with the Ryukyuans from Okinawa (Japan)