diff --git a/presentation/ApplicationCategories.R b/presentation/ApplicationCategories.R
index be6b348..4cd7128 100644
--- a/presentation/ApplicationCategories.R
+++ b/presentation/ApplicationCategories.R
@@ -71,6 +71,12 @@ rows_os_manufacturer <- grepl(grep_pattern, df_app_categories$package_name)
 df_app_categories[!rows_os_manufacturer, ] %>%
   filter(play_store_genre == "not_found")
 
+# Also check the relationship between is_system_app and System category.
+tbl(con, "applications") %>% 
+  filter(is_system_app, play_store_genre != "System") %>% 
+  count()
+# They are perfectly correlated.
+
 # Manually classify apps
 df_app_categories[df_app_categories$play_store_genre == "not_found",] <- 
   df_app_categories %>%