Size 6 or 8 didn't even exist back in the 1950s! Size 10 was about the lowest available size; the few size 8s were smaller than size 6 was in the 1980s, or size 0 is today! I wore size 6 in the 1980s, for my 25" waist and 35" hips. My weight and measurements have not changed, but now size 6 is for people at least 3-4" bigger both measurements, and I've run across size 0s so baggy on me that I could slip them off without unbuttoning or unzipping them. Vanity sizing is out of control, as are dishonest size charts (eg a  clothier who list size 6 as for 27" waist /37" hips, but the tape measure shows  their size 6is really for 30" waist/ 40" hips.)