<prompt> Translate the following text to EnglishSekta ya HH-to-NHH, ambayo inajumuisha barua ya malipo, imepata kupungua kwa kiasi kikubwa kuliko barua ya kibinafsi katika miaka ya 90.  <response>: The HH-to-NHH sector, which consists mainly of payment mail, has experienced a steeper volume decline than personal mail in the 90s. 