Half of Turku's population growth went to two postal code areas
Turku's population grew by 13,111 in 2019–2024, and half of that growth went to two postal code areas. Turku Keskus (20100), the city-centre area, grew by 3,528 and Iso-Heikkilä (20200) by 3,234, 6,762 between them.
Iso-Heikkilä is the more unusual of the two. Its population more than doubled, from 2,619 to 5,853, and its dwelling count rose from 2,087 to 5,145. The same postal code area also includes Linnanfältti, whose residents the statistics do not separate from the rest of the area. The relative growth was 123.5%, the third largest in Finland among the 1,451 postal code areas with at least 500 residents in 2019. Only Helsinki's Keski-Herttoniemi - Roihupelto (00880) and Kalasatama - Kyläsaari (00580) grew faster.
Turku Keskus grew differently: from a large base, 27,628 residents, by 12.8%. It gained 2,990 dwellings.
The third-largest gain was in Nummi-Ylioppilaskylä (20540), 1,684 residents. Of Turku's 26 inhabited postal code areas, 20 grew and six lost a combined 517 residents. Martti-Korppolaismäki (20810) lost the most, 206 residents or 1.2% of its 17,061 in 2019.
Two more Turku areas grew among Finland's fastest. Of the 1,451 postal code areas with at least 500 residents in 2019, Skanssi (20730) grew the 8th fastest (+81.5%) and Pitkämäki-Muhkuri (20250) the 11th fastest (+74.2%). Both started small: in 2019 Skanssi had 764 residents and Pitkämäki-Muhkuri 733. They grew by 623 and 544.
There's a catch. The postal code area figures come from Statistics Finland's Paavo dataset, and they add up to 2,237 fewer residents than Turku's official population in 2019 and 2,280 fewer in 2024. Paavo leaves out residents without coordinates, and postal code and municipal boundaries do not always line up. That is why the areas' combined growth, 13,068, falls 43 short of the official 13,111. Every year is computed on the same, latest postal code division, so boundary changes do not show up as growth or decline.
Check it yourself. Population and dwelling counts for all 26 inhabited areas in 2019 and 2024 are in the downloadable CSV file. The chart and the file are free to reuse (CC BY 4.0).