<prompt> Translate the following text to EnglishHata hivyo, waandishi hawawezi kueleza kwa nini asilimia ya Ureno ya gharama ya usindikaji wa barua ni chini sana ikilinganishwa na posts nyingine katika sampuli.  <response>: Nevertheless, the authors cannot explain why Portugals percentage of mail processing cost is so low in comparison to the other posts in the sample. 