diff --git a/src/agora/io/signal.py b/src/agora/io/signal.py
index 6b9457bd77b91d9303758168188603ce7d5b728f..03dc98fc162efce983aa4be45a73d162ca0c5d6e 100644
--- a/src/agora/io/signal.py
+++ b/src/agora/io/signal.py
@@ -107,7 +107,9 @@ class Signal(BridgeH5):
         with h5py.File(self.filename, "r") as f:
             return list(f.attrs["channels"])
 
-    def retained(self, signal, cutoff=0.8):
+    def retained(
+        self, signal, cutoff=global_parameters.signal_retained_cutoff
+    ):
         """
         Load data (via decorator) and reduce the resulting dataframe.
 
diff --git a/src/aliby/global_parameters.py b/src/aliby/global_parameters.py
index 92b58f8969de09ee31c558019ccabe52a01338c5..9fa29a4728780ef10c757a8273f8d36c496d472c 100644
--- a/src/aliby/global_parameters.py
+++ b/src/aliby/global_parameters.py
@@ -36,3 +36,6 @@ fluorescence_functions = [
     "imBackground",
     "max5px_median",
 ]
+
+# default fraction of time a cell must be in the experiment to be kept by Signal
+signal_retained_cutoff = 0.8