Chūgoku Mountains
One-third of the prefecture's population is concentrated in the Izumo-Matsue area. Otherwise, over two-thirds of the population is on the coastline. The reason is that the Chūgoku Mountains make the land inland harder to inhabit. The capital, Matsue, has the smallest population out of all the 47 prefectural capitals. Shimane has also the largest percentage of the elderly. The province had an estimated 743 centenarians per million inhabitants in September 2010, the highest ratio in Japan, overtaking Okinawa Prefecture (667 centenarians per million).