diff --git a/app.js b/app.js
index ad9a93a..fd1ef23 100644
--- a/app.js
+++ b/app.js
@@ -1 +1,46 @@
 'use strict';
+const fs = require('fs');
+const readline =require('readline');
+const rs = fs.createReadStream('./popu-pref.csv');
+const rl = readline.createInterface({input: rs, output: {}});
+const prefectureDataMap = new Map(); // key: 都道府県 value: 集計データのオブジェクト
+rl.on('line', lineString =>{
+   const columns = lineString.split(',');
+   const year = parseInt(columns[0]);
+   const prefecture = columns[1];
+   const popu = parseInt(columns[3]);
+   if (year === 2010 || year === 2015) {
+    
+        let value = null;
+        if (prefectureDataMap.has(prefecture)) {
+          value = prefectureDataMap.get(prefecture);
+        } else {
+          value = {
+            popu10: 0,
+            popu15: 0,
+            change: null
+          };
+        }
+        if (year === 2010) {
+          value.popu10 = popu;
+        }
+        if (year === 2015) {
+          value.popu15 = popu;
+        }
+        prefectureDataMap.set(prefecture, value);
+       }
+     });
+    rl.on('close', () => {
+      for (const [key, value] of prefectureDataMap){
+        value.change = value.popu15 / value.popu10;
+      }
+      const rankingArray = Array.from(prefectureDataMap).sort((pair1,pair2)=>{
+        return pair1[1].change - pair2[1].change;
+      });
+      const rankingString = rankingArray.map(([key, value],i)=>{
+        return (
+            `${i + 1}位 ${key}: ${value.popu10}=>${value.popu15} 変化率: ${value.change}`
+        );
+      });
+      console.log(rankingString);
+    });