diff --git a/README.md b/README.md
index 62265ad..a042fc8 100644
--- a/README.md
+++ b/README.md
@@ -60,6 +60,8 @@ cd reports/time-horizon-1-0
 dvc repro
 
 # Run the time-horizon-1-1 report
+# NOTE: time-horizon-1-0 must be reproduced first, as time-horizon-1-1
+# depends on its outputs (e.g. data/wrangled/logistic_fits/headline.csv).
 cd reports/time-horizon-1-1
 dvc repro
 ```
diff --git a/src/horizon/wrangle/logistic.py b/src/horizon/wrangle/logistic.py
index ef0cd94..55aca0a 100644
--- a/src/horizon/wrangle/logistic.py
+++ b/src/horizon/wrangle/logistic.py
@@ -117,7 +117,7 @@ def agent_regression(
             values.extend([0, 0, 0])  # p{n}, p{n}q10, p{n}q90
         result = pd.Series(values, index=indices)  # type: ignore[reportCallIssue]
         if include_empirical_rates:
-            result = result._append(empirical_rates)
+            result = pd.concat([result, empirical_rates])
         return result
 
     model = logistic_regression(
@@ -160,7 +160,7 @@ def agent_regression(
 
     result = pd.Series(values, index=indices)  # type: ignore[reportCallIssue]
     if include_empirical_rates:
-        result = result._append(empirical_rates)
+        result = pd.concat([result, empirical_rates])
     return result