diff --git a/app/controllers/work_records_controller.rb b/app/controllers/work_records_controller.rb
index e5d9cef..3a2caf8 100644
--- a/app/controllers/work_records_controller.rb
+++ b/app/controllers/work_records_controller.rb
@@ -43,7 +43,7 @@ def index
     
     @accord_sum = @work_records.inject(0.0) {|sum, wr| sum += wr.accord_all_groups }
     @all_work_time_sum = @work_records.inject(0.0) {|sum, wr| sum += wr.all_work_time }
-    @productivity_sum = @accord_sum/@all_work_time_sum
+    @productivity_sum = @all_work_time_sum > 0 ? @accord_sum/@all_work_time_sum : 0.0
     
     store_target_location
     provide_print_version_if_requested