diff --git a/app/broadcast_areas/__init__.py b/app/broadcast_areas/__init__.py
index 338763fe3..54022216b 100644
--- a/app/broadcast_areas/__init__.py
+++ b/app/broadcast_areas/__init__.py
@@ -74,12 +74,14 @@ class BroadcastArea(SortableMixin):
         # https://www.pivotaltracker.com/story/show/174837293
         return self._count_of_phones or 0
 
-    @property
+    @cached_property
     def phone_density(self):
         return self.count_of_phones / self.polygons.estimated_area
 
     @property
     def estimated_bleed_in_m(self):
+        if self.phone_density < 1:
+            return Polygons.approx_bleed_in_degrees * Polygons.approx_metres_to_degree
         estimated_bleed = 5_900 - (math.log(self.phone_density, 10) * 1_250)
         return max(500, min(estimated_bleed, 5000))
 
diff --git a/tests/app/broadcast_areas/test_broadcast_area.py b/tests/app/broadcast_areas/test_broadcast_area.py
index 705916cb5..02d84f3da 100644
--- a/tests/app/broadcast_areas/test_broadcast_area.py
+++ b/tests/app/broadcast_areas/test_broadcast_area.py
@@ -334,6 +334,10 @@ def test_phone_density(
         # Highland (least dense in UK)
         'lad20-S12000017', 5_000, 0.0449
     ),
+    (
+        # No population data available
+        'test-santa-claus-village-rovaniemi', 1_500, 0.01347
+    )
 ))
 def test_estimated_bleed(
     area, expected_bleed_in_m, expected_bleed_in_degrees,