diff --git a/.gitignore b/.gitignore
index 57872d0..ca08cc4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /vendor/
+/data/*.csv
diff --git a/data/README.txt b/data/README.txt
new file mode 100644
index 0000000..94f4ade
--- /dev/null
+++ b/data/README.txt
@@ -0,0 +1,2 @@
+domainmap.txt maps the user's domain from their email address to an identifier.
+usermap.txt maps a user's FULL email address to an identifier.