The HNH angle value is higher than HPH, HAsH and HSbH angles. Why?

Among the group 15 elements, N has the highest electronegativity, because of which there is high electron density around N. This causes repulsion between the electron pairs around causing high HNH angle value. As we go down the group, the electronegativity of the elements decease and the bond angle also decreases due to lesser repulsion.