in Varsinais-Suomi:Coastal municipalities in Varsinais-Suomi which also include some islands:Island municipalities in Åland:Coastal municipalities in Uusimaa which also include some islands:''' Hanko Raseborg The archipelago continues further to the east in Uusimaa, but Hanko is traditionally seen as a dividing point between the Archipelago Sea and the Gulf of Finland. Demographics The number of permanent residents on the islands is roughly 60,000, with 27,000 of them living in Åland. Also outside Åland most of the area has been more or less monolingually Swedish-speaking, now officially bilingual with a Swedish-speaking majority. The northern part of the area is monolingually Finnish-speaking. Throughout its history the population of the Archipelago Sea has varied significantly. The population increased until the first half of the 16th century. After that the population went into decline as the carrying capacity of the environment was reached and wars and pestilence took their toll on the people. In the 19th century the population increased sharply as new, more efficient fishing methods were introduced. In the 20th century the population went into decline again, especially on smaller islands, due to rapid urbanization. Many smaller islands became completely uninhabited. During the recent decades increasing number of summer residences in the archipelago have revitalized some areas. Many Finns have summer residences on the islands in the area, known for its natural beauty. Due to this the population of many islands can double or more during the summer. Although having a summer cottage in the archipelago is more common among the Swedish-speaking, the Swedish-speaking are a small minority on the mainland, and so most summer residents are Finnish-speaking, in contrast to the permanent residents. Kultaranta, the official summer residence of the president of Finland is on the island of Luonnonmaa in Naantali. An anomalous feature in the demographics in the archipelago is the number of twins. The tendency for non-identical twin births is partly hereditary, and the necessary genes are prevalent in the archipelago. In the 18th and 19th centuries the proportion of twin births was greater than anywhere in Europe, and enormously higher than in continental Finland. The reason for this was fishing. Fish is an excellent source of protein and unsaturated fat. It was also available even when crops failed. Hence having twins maximizes lifetime reproductive success. Economy and communications The islands generally enjoy a high standard of living comparable to that of continental Finland. Fishing and fish processing are major