抄録
The population of Japan began to decrease in 2005, and this trend is predicted to continue in the future. The nation-level population decrease can be mostly explained by a decreased fertility rate, while out-migration played an important role in the population decreases seen in prefectures in nonmetropolitan regions. This study investigated the fertility and in-migration rates required to maintain the population size in the Tohoku region. Six prefectures (Aomori, Iwate, Miyagi, Akita, Yamagata, and Fukushima) and Sendai City were targeted. Using the cohort component method, population sizes after 50 years were projected by assuming various levels of fertility and in-migration rates. A>250% increase in the current fertility rate is needed to avoid population decreases in all prefectures with the exception of Miyagi ; the required level was the highest in Akita (378%). On the other hand, if the in-migration rate could be increased to 200% of the current level, the population of Tohoku would remain at the current size. The fertility and in-migration rates needed to maintain the population of the Tohoku region are unrealistically high ; thus, future strategies based on the population decrease are needed.
