diff --git a/util/summarize.py b/util/summarize.py
new file mode 100644
index 0000000..18ac09a
--- /dev/null
+++ b/util/summarize.py
@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+#
+# Read the git history of the `dashboard/dashboard-results.yml` file,
+# and generate a table of passing check counts on each date.
+
+import csv
+import subprocess
+import yaml
+
+from collections import defaultdict
+from datetime import datetime
+
+
+def list_commits(path):
+    """Given a file path,
+    return a list of dates and commit hashes
+    for each commit that modified that file."""
+    process = subprocess.run(
+        ["git", "log", "--follow", "--reverse", "--", path],
+        check=True,
+        text=True,
+        stdout=subprocess.PIPE
+    )
+    commits = []
+    commit = None
+    for line in process.stdout.splitlines():
+        if line.startswith("commit "):
+            commit = line.replace("commit ", "").strip()
+        elif line.startswith("Date: "):
+            date = line.replace("Date: ", "").strip()
+            dt = datetime.strptime(date, '%a %b %d %H:%M:%S %Y %z')
+            ymd = dt.strftime("%Y-%m-%d")
+            commits.append([ymd, commit])
+    return commits
+
+
+def summarize_run(data):
+    """Given a dashboard-results YAML
+    return a dictionary from principles to counts
+    of FP* checks that passed,
+    and the total number of ontologies."""
+    result = defaultdict(int)
+    for ontology in data["ontologies"]:
+        result["total"] += 1
+        if "results" not in ontology:
+            continue
+        for key, value in ontology["results"].items():
+            if not key.startswith("FP"):
+                continue
+            if "status" not in value:
+                continue
+            if value["status"] != "PASS":
+                continue
+            result[key] += 1
+    return result
+
+
+def read_yaml(path, commit):
+    """Given a file path and a commit hash,
+    read the file as YAML and return the contents."""
+    process = subprocess.run(
+        ["git", "show", commit + ":" + path],
+        check=True,
+        text=True,
+        stdout=subprocess.PIPE
+    )
+    return yaml.safe_load(process.stdout)
+
+
+def main():
+    """Read all the versions of dashboard-results
+    in the git history
+    and write a `summary.tsv` with counts by date."""
+    path = "dashboard/dashboard-results.yml"
+    commits = list_commits(path)
+    rows = []
+    for (date, commit) in commits:
+        data = read_yaml(path, commit)
+        row = summarize_run(data)
+        row["date"] = date
+        rows.append(row)
+
+    fieldnames = list(rows[-1].keys())
+    fieldnames.sort(key=str.casefold)
+    with open("summary.tsv", "w") as f:
+        w = csv.DictWriter(
+            f, fieldnames=fieldnames, delimiter="\t", lineterminator="\n"
+        )
+        w.writeheader()
+        w.writerows(rows)
+
+
+if __name__ == "__main__":
+    main()