@Shmuel @SuryaKiran @Astounding @ballardw Thanks to all of you. You all pretty much had it right; When I finally looked at the data for one month, Client_Specialty_Flag was in the right order with all of the "Non-Specialty" coming before all "Specialty". Then, when ran for 2 or more months, since I didn't sort it before the data step that I had the by's, the order got messed up as my data had a lot of "Specialty" before "Non-Specialty" within the same by-groups. Thank you everyone for your patience, I learned a lot about by groups/by statement in data step, and sorting.