Taylor is currently ranked 11th in the test rankings and his high score in 2017 was 107 not out against the West Indies.
Runs scored or number of centuries scored is probably a better way to judge a year's work in test cricket.
Williamson (566), Jeet Raval (475) and Tom Latham (457) all scored more test runs than Taylor (408) in 2017. Williamson also had three centuries while Taylor had one.
Williamson was named in the original list of nominees for the sportsman of the year in December but scored one 50 in the subsequent two tests against West Indies.
The other factor around Taylor's misleading test average in 2017 is the opposition. He missed two tests against world number ranked South Africa so his five tests were against the lower ranked Bangladesh and West Indies. All played on home soil. Not exactly testing opposition or conditions.
To his credit Taylor did earn a man of the match award in the second test against the West Indies with a second innings century which set up the victory. That's not enough to earn a Halberg Award nomination though.
Taylor had a more impressive year in the ODI format.
He scored the fifth most ODI runs in world cricket in 2017 with 968 in 20 innings. That's a good chunk of batting to mention his average, so it's worth noting it was 60.50. He scored two centuries, against Australia and South Africa, and seven 50s including a 95 in India which set up a memorable win.
But based on the fact he wasn't originally among the Halberg nominations named in December, the decision is based on his performance in tests. It seems New Zealand Cricket sent in a late nomination for Taylor following the test series.
His 102 not out against South Africa in February was Taylor's 17th ODI century, the most ever by a New Zealander. A true testament to a remarkable career of one of our country's best ever cricketers. However the Halberg Awards is judged on the work of one year and not over a career, so milestones don't count for anything.
There's no doubt Taylor will go down as one of our sporting greats. But 2017 was certainly not one of his great years.