diff --git a/ETA.py b/ETA.py
index 84f5618..5e1d19f 100755
--- a/ETA.py
+++ b/ETA.py
@@ -606,7 +606,7 @@ bias = {
     ),
 }
 
-mean_bias = np.mean( [ bias[ 'top' ] , bias[ 'down' ] ] , axis = 0 )
+mean_bias = bias[ 'down' ]
 
 data[
                            :                       ,