Cost per install is the easiest acquisition number to report and the easiest to misread. A cheap install that never comes back costs more than an expensive one that subscribes.
Put retention next to every CAC
Compare channels on cost per retained user at day 7 and day 30, not on cost per install. The ranking of channels often reverses.
Watch the blend
A blended CAC hides which channels are carrying the others. Read it by channel and by campaign before deciding where the next budget goes.
