diff --git a/server/nightr/app.py b/server/nightr/app.py
index b8f788b..b84d768 100644
--- a/server/nightr/app.py
+++ b/server/nightr/app.py
@@ -78,13 +78,13 @@ def probabilities():
             prediction["night"] = not prediction["night"]
 
     # Calculate contributions of predictions
-    consensus_weight_sum = sum(p["weight"] for p in predictions if p["night"] == night)
+    weight_sum = sum(p["weight"] for p in predictions)
     for prediction in predictions:
-        # If this prediction agrees with the consensus it contributed
-        if prediction["night"] == night:
-            prediction["contribution"] = prediction["weight"] / consensus_weight_sum
-        else:
-            prediction["contribution"] = 0.0
+        prediction["contribution"] = prediction["weight"] / weight_sum
+
+        # If this prediction disagrees with the consensus it contributed negatively
+        if prediction["night"] != night:
+            prediction["contribution"] *= -1
 
     return jsonify({
         "predictions": predictions,