<prompt> Translate the following text to EnglishHii ni kwa sababu ya: a Mshuko wa mapato kutoka kwa sekta ya kaya; b Kuongezeka kwa, kwa thamani ya jumla, elasticity ya bei ya kibinafsi; c Kuongezeka kwa kubadilishana kwa matumizi ya posta na matumizi ya kompyuta; d Kuongezeka kwa kubadilishana kati ya matumizi ya posta na matumizi ya simu.  <response>: they illustrate 1 Decline in revenue share from household sector 2 Increasing, in absolute value, own-price elasticity 3 Increasing substitutability away from postage consumption with computer use 4 Increasing substitutability between postage and telephone consumption. 