[2] (Annual average: 4.9 m/s or 18 km/h or 11 mph) Per Japanese census data, the population of Rumoi is as shown below.

[6] Rumoi has a mayor-council form of government with a directly elected mayor and a unicameral city council of 14 members.

In terms of national politics, the city is part of the Hokkaidō 10th district of the lower house of the Diet of Japan.

After the depletion of herring resources in 1950, Mitsui & Co. and others began importing fish roe and other products from overseas for seafood processing companies, and lumber processing companies in the city also began importing northern timber in the 1950s, so the city's economy has been based on commerce, fishing and mining since 1950.

In the 1960s, the coal mines were closed and in the 1970s, local seafood processing companies gradually lost market share to factories in Sapporo and the Tokyo metropolitan area, which are located near major consumer areas.

By the 1990s, wood processing companies went out of business or moved overseas, almost eliminating economic activity in the city.

The Rumoi Main Line also formerly ran to Mashike, located southwest of Rumoi, until December 4, 2016, when the Mashike-Rumoi section, including Segoshi and Reuke station, was closed owing to declining passenger numbers.