diff --git a/scanner/main.ts b/scanner/main.ts
index 74b31a9..b649e6e 100644
--- a/scanner/main.ts
+++ b/scanner/main.ts
@@ -1,6 +1,7 @@
 import Bottleneck from "bottleneck";
 import specs from 'browser-specs' assert { type: "json" };
 import fs from 'node:fs/promises';
+import { mean, quantile } from 'simple-statistics';
 import octokit from './third_party/octokit-cache.js';
 
 const ghLimiter = new Bottleneck({
@@ -20,54 +21,104 @@ interface IssueSummary {
   pull_request?: { draft: boolean };
   milestone?: string;
   labels: string[];
+  ageAtCloseMs?: number;
+};
+
+interface AgeStats {
+  count: number;
+  mean: number;
+  [percentile: string]: number;
 };
 
 interface RepoSummary {
-  cached_at: number;
+  cachedAt: number;
   org: string;
   repo: string;
   issues: IssueSummary[];
   labelsPresent: boolean;
+  ageAtCloseMs?: AgeStats;
+  openAgeMs?: AgeStats;
+}
+
+interface GlobalStatsInput {
+  closeAgesMs: number[];
+  openAgesMs: number[];
 }
 
-async function analyzeRepo(org: string, repo: string): Promise<RepoSummary> {
+function ageStats(arr: number[]): AgeStats | undefined {
+  if (arr.length === 0) {
+    return undefined;
+  }
+  const result = {
+    count: arr.length,
+    mean: mean(arr),
+  }
+  const percentiles = [10, 25, 50, 75, 90];
+  quantile(arr, percentiles.map(p => p / 100)).forEach((q, i) => {
+    result[percentiles[i]] = q;
+  });
+  return result;
+}
+
+async function analyzeRepo(org: string, repo: string, globalStats: GlobalStatsInput): Promise<RepoSummary> {
+  let result: RepoSummary | null = null;
   try {
-    const cachedRepo = JSON.parse(await fs.readFile(`summaries/${org}/${repo}.json`, { encoding: 'utf8' }));
-    if (Date.now() - cachedRepo.cached_at < 60 * 60 * 1000) {
-      return cachedRepo;
-    }
+    result = JSON.parse(await fs.readFile(`summaries/${org}/${repo}.json`, { encoding: 'utf8' }),
+      (key, value) => {
+        if (['created_at', 'closed_at'].includes(key)) {
+          return new Date(value);
+        }
+        return value;
+      });
   } catch {
     // On error, fetch the body.
   }
-  const result: RepoSummary = {
-    cached_at: Date.now(),
-    org, repo,
-    issues: [],
-    labelsPresent: false
-  };
-
-  for (const issue of await getIssues(octokit, org, repo)) {
-    const info: IssueSummary = {
-      number: issue.number,
-      url: issue.html_url,
-      title: issue.title,
-      created_at: new Date(issue.created_at),
-      labels: issue.labels?.map(label => label.name) ?? [],
+  if (!result || Date.now() - result.cachedAt > 60 * 60 * 1000) {
+    result = {
+      cachedAt: Date.now(),
+      org, repo,
+      issues: [],
+      labelsPresent: false
     };
-    if (issue.closed_at) {
-      info.closed_at = new Date(issue.closed_at);
-    }
-    if (issue.pull_request) {
-      info.pull_request = { draft: issue.pull_request.draft }
-    }
-    if (issue.milestone) {
-      info.milestone = issue.milestone.title;
+
+    for (const issue of await getIssues(octokit, org, repo)) {
+      const info: IssueSummary = {
+        number: issue.number,
+        url: issue.html_url,
+        title: issue.title,
+        created_at: new Date(issue.created_at),
+        labels: issue.labels?.map(label => label.name) ?? [],
+      };
+      if (issue.closed_at) {
+        info.closed_at = new Date(issue.closed_at);
+      }
+      if (issue.pull_request) {
+        info.pull_request = { draft: issue.pull_request.draft }
+      }
+      if (issue.milestone) {
+        info.milestone = issue.milestone.title;
+      }
+      result.issues.push(info);
     }
-    result.issues.push(info);
+  }
 
-    await fs.mkdir(`summaries/${org}`, { recursive: true });
-    await fs.writeFile(`summaries/${org}/${repo}.json`, JSON.stringify(result, undefined, 2));
+  const closeAgesMs: number[] = [];
+  const openAgesMs: number[] = [];
+  for (const issue of result.issues) {
+    if (issue.closed_at) {
+      closeAgesMs.push(issue.closed_at.valueOf() - issue.created_at.valueOf());
+    } else {
+      openAgesMs.push(result.cachedAt - issue.created_at.valueOf());
+    }
   }
+  result.ageAtCloseMs = ageStats(closeAgesMs);
+  result.openAgeMs = ageStats(openAgesMs);
+  globalStats.closeAgesMs.push(...closeAgesMs);
+  globalStats.openAgesMs.push(...openAgesMs);
+
+  await fs.mkdir(`summaries/${org}`, { recursive: true });
+  await fs.writeFile(`summaries/${org}/${repo}.json`, JSON.stringify(result, undefined, 2));
+
   return result;
 }
 
@@ -93,7 +144,14 @@ async function main() {
     const [org, repo] = parts;
     githubRepos.push({ org, repo });
   }
-  await Promise.all(githubRepos.map(({ org, repo }) => analyzeRepo(org, repo)));
+
+  const globalStats: GlobalStatsInput = { openAgesMs: [], closeAgesMs: [] };
+  await Promise.all(githubRepos.map(({ org, repo }) => analyzeRepo(org, repo, globalStats)));
+
+  await fs.writeFile("summaries/global.json", JSON.stringify({
+    ageAtCloseMs: ageStats(globalStats.closeAgesMs),
+    openAgeMs: ageStats(globalStats.openAgesMs),
+  }, undefined, 2));
 }
 
 await main();
diff --git a/scanner/package.json b/scanner/package.json
index cb949c8..dfe8bdd 100644
--- a/scanner/package.json
+++ b/scanner/package.json
@@ -16,7 +16,8 @@
     "@octokit/plugin-throttling": "^8.0.0",
     "bottleneck": "^2.19.5",
     "browser-specs": "^3.62.0",
-    "node-fetch": "^3.3.2"
+    "node-fetch": "^3.3.2",
+    "simple-statistics": "^7.8.3"
   },
   "devDependencies": {
     "@tsconfig/node20": "^20.1.2",
diff --git a/scanner/pnpm-lock.yaml b/scanner/pnpm-lock.yaml
index e7c0850..e5c3d13 100644
--- a/scanner/pnpm-lock.yaml
+++ b/scanner/pnpm-lock.yaml
@@ -20,6 +20,9 @@ dependencies:
   node-fetch:
     specifier: ^3.3.2
     version: 3.3.2
+  simple-statistics:
+    specifier: ^7.8.3
+    version: 7.8.3
 
 devDependencies:
   '@tsconfig/node20':
@@ -182,6 +185,10 @@ packages:
       wrappy: 1.0.2
     dev: false
 
+  /simple-statistics@7.8.3:
+    resolution: {integrity: sha512-JFvMY00t6SBGtwMuJ+nqgsx9ylkMiJ5JlK9bkj8AdvniIe5615wWQYkKHXe84XtSuc40G/tlrPu0A5/NlJvv8A==}
+    dev: false
+
   /typescript@5.2.2:
     resolution: {integrity: sha512-mI4WrpHsbCIcwT9cF4FZvr80QUeKvsUsUvKDoR+X/7XHQH98xYD8YHZg7ANtz2GtZt/CBq2QJ0thkGJMHfqc1w==}
     engines: {node: '>=14.17'}