diff --git a/outages/README.md b/outages/README.md
index 2b802e053..557ee553d 100644
--- a/outages/README.md
+++ b/outages/README.md
@@ -4,3 +4,11 @@ A collection of large cloud outages collected by year which to serve as a data b
 for the argument against believing in cloud SLAs. Not that I'm against using the cloud,
 but knowing there will be several days outage a year with a certain probability despite
 any promised SLA is important.
+
+### Listing criteria
+
+To understand which outages are listed and why others are not. The criteria are roughly
+
+- outage is global
+- or very long >1h
+- or causing a complete service loss in a region