Korea's local administrative system is defined in the Special Act on Reform of the Local Administrative System, in force from 2013, as the tiered structure of local self-government and administration, the jurisdiction of local governments, and the division of functions among the state, provinces and metropolitan cities, and cities, counties and districts. Article 3 of the Act sets the direction: residents' convenience, national and local competitiveness, a better fit of tiers and scale, and neighborhood self-government.

In principle a single-tier arrangement, in which one government handles all local work, avoids overlap; in practice a two-tier arrangement is common, and with it come duplicated tasks, blurred responsibility, and slower central oversight. Today's map still carries traces of Joseon's two-level system and of the colonial division into thirteen provinces — the source's slip 'ilje gamjeonggi' is the colonial period, ilje gangjeomgi — and of 1946, when Jeju was separated from South Jeolla as a province and Seoul was taken out of Gyeonggi as a special city.

The case at the center is Changwon. In the early 1900s the three places had been one unit, Changwon-bu, then were split into Changwon, Masan and Jinhae. Under the Lee Myung-bak government, incentives were offered for mergers. A Ministry of Public Administration survey of 1,000 residents in each city found a majority in favor overall, though Changwon and Jinhae were split at about six to four, while support in Masan reached 87 percent.

A 2009 telephone survey by the Gyeongnam Sinmun and Q&A Research, 600 residents in each city, listed falling fiscal independence, resident conflict, weaker services and a weaker local economy among the reasons for opposition. In November 2009 the ministry said it would designate a unified city if the three councils agreed, and offered to cover 10 percent of any fiscal shortfall. Changwon and Jinhae councils, which had wanted a referendum, changed position; Masan's council was split.

In a 2009 plenary sitting, yes votes were more than three times the noes. A mayoral election was held in June 2010, and the unified city was launched in July. By 2019 its population was already over 1.05 million. Surface numbers looked strong, and the city received special central support, but trust fell because the merger went ahead without a referendum, and fights followed over the city hall, a baseball stadium and other sites.

In a study discussed in the Gyeongnam Domin Ilbo on 10 July 2017, seven years after the launch, Seoul National University professor Im Dong-geun found no meaningful synergy: migration and traffic flows had not really changed, the three areas still lived apart in practice, and working-age people were leaving Masan. The writer's own view is that the center pushed the merger as a showcase, and that the councils and residents never held the last word.