The current 3,228 cities, towns and villages nationwide could conceivably be merged into just 622 entities, according to the Public Management, Home Affairs, Posts and Telecommunications Ministry.
The ministry's recent report of simulated mergers of cities, towns and villages has been submitted to a Liberal Democratic Party committee on local administration research. The report was compiled with the cooperation of all 47 prefectural governments.
The ministry's simulation suggests the number of administrative units throughout Japan could be reduced to 1,140, but potentially to as few as 622.
In its guidelines for administrative reform, the central government aims to reduce the number of city, town and village administrations to about 1,000, and the simulated level of 1,140 is considered to be close enough to that goal, the report says.
By prefecture, Gunma -- one of the most reluctant to adopt such reforms -- and Fukushima could potentially each slim down their administrative units by more than 85 percent, the report says.
The 70 administrative units in Gunma could be reduced to just 10, and the 90 units in Fukushima merged into 12.
The 37 cities, towns and villages in Kanagawa Prefecture could be merged into 10, while Hokkaido's 212 administrative units -- the largest number in the country -- could be slashed to 72, the report says.
A ministry official said the simulation is merely a reference point, adding that the areas designated to be merged by prefectural governments will not necessarily be the same as those selected in the report.
The central government, which has promoted such mergers as part of streamlining efforts to promote efficiency, has provided financial incentives to cities, towns and villages that have merged with neighboring municipalities.