minolta xgm underexposure

Hi All, I'll keep it brief, My Minolta XGM (1982) has underexposed a new, ISO 200 36 exp. Kodacolor roll (it's first roll in 10 years), 100% consistently - by around 1 stop. Film technology presumably has improved and as such 200 ISO is the new 100? I'm considering setting the ISO to 100 on...