Horace Dediu:
[C]apital spending has provided reliable foreshadowing of iOS device production. This is itself because Apple invests in the equipment used in the manufacturing processes for its devices. The more spending on equipment, the more production capacity is brought to bear and the more units are produced. Since iOS devices tend to be supply constrained, the more units are produced then the more are sold.
It’s one thing to have a hot product, it’s another thing to be able to (mostly) keep up with such high demand while also turning a crazy profit.
The pieces are in place for continuing the existing rate of growth.
Success breeds success. And in this case, the more successful Apple is the more successful they can continue to be.