The PGA Tour recognizes only scoring averages that were eligible for the Vardon Trophy in determining the tour record for best seasonal scoring average. For that reason, Byron Nelson's 1945 scoring average of 68.34 does not appear on the lists below (the Vardon Trophy was not awarded in 1945).
This also explains why Jack Nicklaus does not appear here. Nicklaus had the lowest scoring average eight times in his career, but all those averages are considered "unofficial" because Nicklaus was never eligible for the Vardon Trophy (mostly due to playing too few rounds).
So, here are the official PGA Tour scoring records, taken only from seasons that qualified for the Vardon Trophy:
Lowest Non-Adjusted Vardon Trophy Scoring Averages
68.17 - Tiger Woods, 2000
68.87 - Tiger Woods, 2001
69.00 - Tiger Woods, 2002
69.03 - Davis Love III, 2001
69.11 - Vijay Singh, 2003
69.11 - Tiger Woods, 2005
69.16 - Phil Mickelson, 2001
69.19 - Vijay Singh, 2004
69.23 - Sam Snead, 1950
69.28 - Jim Furyk, 2003
69.30 - Ben Hogan, 1948
69.33 - Greg Norman, 1994
69.34 - Vijay Singh, 2001
69.37 - Sam Snead, 1949
Lowest Adjusted Vardon Trophy Scoring Averages
(Note: Adjusted averages have only been calculated since 1988)
67.79 - Tiger Woods, 2000
68.41 - Tiger Woods, 2003
68.43 - Tiger Woods, 1999
68.56 - Tiger Woods, 2002
68.65 - Vijay Singh, 2003
68.66 - Tiger Woods, 2005
68.81 - Greg Norman, 1994
68.81 - Tiger Woods, 2001
68.84 - Vijay Singh, 2004
68.86 - Jim Furyk, 2006
68.90 - Greg Norman, 1993
Source: PGA Tour
