diff --git a/lib/timecost/author_list.rb b/lib/timecost/author_list.rb
index 355952e..966eaaa 100644
--- a/lib/timecost/author_list.rb
+++ b/lib/timecost/author_list.rb
@@ -30,5 +30,9 @@ module TimeCost
 		def parse author
 			return @author_to_id[author]
 		end
+
+		def size
+			return @author_to_id.keys.size
+		end
 	end
 end