I generally play around with the numbers and try to use an average going forward. 3-4 percent is fairly safe and would account for a hiring slow down at some point either due to economic reasons or internal reasons. I assume at that point, the upgrades will also start trending towards the 55 percent range.
Looking at aircraft deliveries going forward, you have to assume that we are going to grow at a glacial clip for the next few years, anyway, even if many of those acquisitions are for 700 retirements.
I just flew a China Eastern 700 on my last trip that we have owned for less than 3 months (the cigarette tar stains on the overhead panel are a dead giveaway), so we are still slowly acquiring used airplanes as well.