diff --git a/app.js b/app.js
index ad9a93a..55e7bca 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});
+const prefectureDataMap = new Map();
+
+rl.on("line", (lineString) => {
+  const columns = lineString.split(",");
+  const year = parseInt(columns[0]);
+  const prefecture = columns[1];
+  const popu = parseInt(columns[3]);
+  if (year === 2016 || year === 2021) {
+    let value = null;
+    if (prefectureDataMap.has(prefecture)) {
+      value = prefectureDataMap.get(prefecture)
+    } else {
+      value = {
+        before: 0,
+        after: 0,
+        change: null
+      }
+    };
+    if (year === 2016) {
+      value.before = popu;
+    };
+    if (year === 2021) {
+      value.after = popu;
+    };
+    prefectureDataMap.set(prefecture, value);
+  }
+
+});
+rl.on("close", () => {
+  for (const [key, value] of prefectureDataMap) {
+    value.change = value.after / value.before
+  }
+  
+  const rankingArray = Array.from(prefectureDataMap).sort((pair1, pair2) => {
+    return pair1[1].change - pair2[1].change;
+  });
+  const rankingString = rankingArray.map(([key, value], i) => {
+    return `${++i}位 ${key}: ${value.before} => ${value.after} 変化率: ${value.change}`
+  });
+  console.log(rankingString);
+});
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