diff --git a/src/mapper.rs b/src/mapper.rs
index 82f9e099..40e2968f 100644
--- a/src/mapper.rs
+++ b/src/mapper.rs
@@ -1454,10 +1454,9 @@ where
 /// compute dropoff of the first (top) NAM
 fn top_dropoff(nams: &[Nam]) -> f32 {
     let n_max = &nams[0];
-    if n_max.anchors.len() <= 2 {
-        1.0
-    } else if nams.len() > 1 {
-        nams[1].anchors.len() as f32 / n_max.anchors.len() as f32
+    if nams.len() > 1 {
+        debug_assert!(n_max.score > 0.0);
+        nams[1].score / n_max.score
     } else {
         0.0
     }