Khat
Some studies done in 2001 estimated that the income from growing khat was about 2.5 million Yemeni rials per hectare, while it was only 0.57 million rials per hectare if fruits were grown.  This is a strong reason farmers prefer to grow khat over coffee and fruits.  It is estimated that between 1970 and 2000, the area on which khat was cultivated grew from 8,000 hectares to 103,000 hectares.