https://www.google.com/amp/s/withnews.jp/amp/article/f0180202001qq000000000000000W00j10301qq000016669A#ampshare=https://withnews.jp/article/f0180202001qq000000000000000W00j10301qq000016669A
https://mainichi.jp/graphs/20180416/hpj/00m/010/003000g/4
https://r.nikkei.com/article/DGXMZO2948404017042018000000?s=1