Rather than take the greater of either waist or hip measurement
and dividing it by two, I measure around the back of the hips
from where I want my pleats to start and end. This tells me
exactly how much fabric will be in the pleats, which is more than
going by half the total measurement. By the way, my waist is
the same size as my hips, but I still have a taper in the pleats
from the hips to waist. This is because my waist sticks out
the front, not the back.