Depends on the year and the service. I speak for my own experience in the Air Force only...we are somewhat well insulated from the job market at large. Things that affect our manning more are personnel policies (how often you move, how often you deploy, the toughness of promotion to Lt Col, assignment location) and poor leadership in some areas (poor flight/squadron/group commanders).
In our service, pharmacists compete against other healthcare officers that don't have their own "Corps." Physicians, nurses, administrators and dentists all have their own corps. Promotion opportunities for Physicians and Dentists are nearly unlimited (they are not limited by DOPMA.)
Administrators have their own corps and promote fairly well (65-70% to O5 depending on year.) Nurses are a little less well off, with promotion to O5 usually in the 55-60% range. Everyone else, called BSCs (to include pharmacists) have the lowest promotion rate as a Corps in the entire Air Force. Last year, that promotion rate (in the zone) was around 40%. It historically has been a tick higher than that.
My unscientific view is that pharmacists perform average to slightly below average promoting to Lt Col when compared to the average BSC.
If you don't promote to O5, your chances of retiring as a BSC without prior military experience is a coin flip.
That being said, I know there were a fair number of positions for pharmacists in our service to start their service this summer.