Why do people on this board spend so much time talking about which top-10 or top-15 departments are on the decline and on the upswing? I've been a sociologist long enough (15 years) to know that these things ebb and flow over time. Princeton loses a couple people, then a few years later, gains a couple big names. They all do it.
The short-term focus on status and position is destructive, in my view. Trust me in saying that the search committee doesn't care if your department is down four spots this year when they're deciding about whether to bring you in for an interview. Seriously.
Departments will try to steal good people away from somewhere else-- we all want to surround ourselves with brilliant and productive colleagues-- but the folks I know are not wasting time worrying about moving up one or two spots (or down) in the rankings. Neither are the administrators. The only people who seem to care are anxiety-ridden graduate students who want to believe their department is on the upswing and that it will enhance their job market prospects. It simply won't. Focus on doing high-quality work (something you can control) and stop wasting your time worrying about which department "is more on the decline."