Posted By:
JimCrandellAl,
I looked at 5 popular sets and the evidence suggests the percentage of cards graded psa 8 or better shoots higher as you go through the 50s and 60s.
1951 Bowman--29% PSA 8 and beeter
1955 Topps 20%
1957 Topps 32%
1961 Topps 48%
1967 Topps 61%