Mark Broadie is a professor of Economics at the Graduate School of Business at Columbia University. On top of that, he's an avid golfer and has spent a lot of time analyzing the causes of golfers' success.
After his first article, "Assessing Golfer Performance Using Golfmetrics", which revolutionized golf metrics with the strokes gained metric, he published another article about measuring putting on the PGA Tour.
As in his previous article, he starts by telling us the limitations of current stats for putting:
So, Broadie says we need a better measure of putting skill, and that is putts gained.
Putts gained measures the number of putts better or worse than the field from a given distance.
Putts gained = PGA TOUR average putts to holeout from the distance - Actual putts to holeout
If we add the putts gained for each hole we will get the putts gained for a round, which is a very sound metric of the quality of the putting in that round.