diff --git a/src/industry.h b/src/industry.h
--- a/src/industry.h
+++ b/src/industry.h
@@ -21,6 +21,8 @@
 typedef Pool<Industry, IndustryID, 64, 64000> IndustryPool;
 extern IndustryPool _industry_pool;
 
+static const Year PROCESSING_INDUSTRY_ABANDONMENT_YEARS = 5; ///< If a processing industry doesn't produce for this many consecutive years, it may close.
+
 /**
  * Production level maximum, minimum and default values.
  * It is not a value been really used in order to change, but rather an indicator