Recent lil.erature has shown 1hll.l lile balance spaee llPproach may be a significant a1ternalive lo address several tapies concerning vec· tor optimization. Although this /lew ¡ook also leads lo lhe eflicicnt set and, consequcntly, is equiva.lent lo lhe classical viewpoint, it yields !lew rc:suJts and a1gorithms, as well as !lew economic interpretations, that Illll)' be very usefuJ in theoreticlÚ framc\vorks and practical applications. The present paper racllses on lhe sensitivity of lhe balance set \Ve prove a general envelope theorem th81 yields lhe sensitlvity with respect to lI.ny parameter considere