<prompt> Translate the following text to EnglishKwa mujibu wa utafiti uliofanywa na Umoja wa Posta Ulimwenguni, uzito wa barua kutoka DC hadi IC ni chini ya asilimia 10 hadi 30 ya uzito wa barua kutoka IC hadi IC.  <response>: Further, studies by the Universal Postal Union indicate that the average weight for each shape envelope, flat, packet of mail sent from DCs to ICs is 10 to 30 percent less than the average weight of mail from ICs to ICs. 