A new rule this year allowing golfers to putt with the flagstick in without incurring a penalty is generating serious debate among pros and amateurs. The USGA made the change to help speed up play, but some tour players are leaving the flagstick in because they believe it helps them make more putts. Is this true? USGA officials say the new rule “wasn't based on research but how the game is played.” So Golf Digest asked if I would help them bring some clarity to the issue. Using the golf teams at California Polytechnic State University, plus a lot of physics, engineering and statistics, I methodically analyzed how a putted ball interacts with a flagstick. After numerous tests with real golfers, machines and multiple types of flagsticks, the data is clear: Leaving the flagstick in hurts a putt's chance of being holed much more often than it helps hole putts that otherwise would not have gone in. Only in the rarest of cases is a flagstick going to “catch” a missing putt and drop it in the hole. Even the most highly skilled putter—given standard deviations—is going to hit the flagstick dead-center only 27.6 percent of the time. For that remaining 72.4 percent, the golfer isn't hitting the pin straight-on, and it's always a disadvantage for making putts in these instances.

TOM MASE, a member of the Golf Digest Technical Panel, is a professor of mechanical engineering at California Polytechnic State University. He has spent more than 30 years in academia and in golf research and development. He was co-captain of the golf team at Michigan State in 1980.

THE METHODOLOGY

Photo by Todd Detwiler

Related: More on how we did it

The testing involved college golfers and the Perfect Putter training aid at the Cal Poly golf-team practice facility at Dairy Creek Golf Course. Using the Perfect Putter, putts were rolled for straight-on and off-center impacts and at multiple speeds that ended up 2.5 feet, 4.5 feet and up to 12 feet past the hole. All scenarios were tested in random rounds of 30 putts each.

THE NUMBERS

For putts rolling 2 1/2 feet by the hole, putts aimed to hit the flagstick dead-center or off-center went in the hole every time—with or without the flagstick in. For putts rolling 4 1/2 feet by the hole and aimed to strike the flagstick off-center, 90 percent of putts were holed without the flagstick in. Only 45 percent were made with the flagstick in.

Only in the rarest of cases is a flagstick going to “catch” a missing putt.

STRAIGHT PUTTS

Flagstick in or not, all putts aimed for dead-center went in, even at speeds rolling eight feet past the hole. At nine to 12 feet past, almost all putts missed without a flagstick in. Almost all were made with flagsticks in (fiberglass, tapered).

THREE-PUTT FACTOR

Keeping the flagstick in can help avoid three-putts. The flagstick kills much of the ball's velocity on a putt hit too hard, even a glancing blow. That leaves a shorter second putt—assuming the putt hits that half-inch-wide flagstick.

THE 99.9967% SOLUTION

Based on probability and standard deviation calculations and PGA Tour statistics, the best tour players would strike the flagstick dead-center from 20 to 25 feet about 3.3 percent of the time. If you assume the best pros would rarely roll their first putt nine feet past the hole —perhaps one in a thousand times—that would make leaving the flagstick in a benefit on only .0033 percent of all putts from 20 to 25 feet. And that's for the best pros. For a typical amateur, those percentages are much worse.

DIFFERENT STICKS, SAME EFFECT

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Putts rolling just off-center and 4½ feet beyond the hole were tested with three flagsticks: fiberglass (the one played most often on the PGA Tour), tapered aluminum and multi-diamater aluminum. All measured approximately one-half inch in diameter at green level. Fiberglass, the lightest, had the least negative results with 61 percent made, followed by multi-diameter (38 percent) and then tapered (36 percent). Each was worse than no flagstick (90 percent).

VISUAL AID OR DISTRACTION?

Does leaving the flagstick in provide a visual benefit? Sports-vision experts believe it would, but a test of elite players was inconclusive. A group of 36 elite college golfers hit 25-foot putts at holes with the flagstick in and out. In both situations, the average putt finished about two feet from the hole. Another point to consider: Because putting with the flagstick in is different, its presence could be physically and mentally distracting to your pre-putt routine.

BRYSON'S LOGIC

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Bryson DeChambeau has been an advocate for putting with the flagstick in: “I haven't studied all the variables in this research, but I'm out here doing this, and I know it works. I had a putt in Dubai that was going at least four feet by the hole, and that putt wouldn't have gone in had I not had the flag in. There's more to it than geometry. There's the visual aspect. It allows you to see the target. There are times it helps to leave the flag in, and I know it's more than .0033 percent.”

WIND ADVISORY

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In strong winds, the flagstick can bend, creating more space on one half of the hole and less on the other. In tests, that change opened up one side of the hole by an eighth of an inch—or the size of a golf-ball dimple. Seems inconsequential compared to just pulling out the flagstick, which opens up the entire hole.

A FINAL POINT

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This data argues against leaving the flagstick in. One more reason: Retrieving putts made with the flagstick in also could lead to hole damage.

SEE FULL TESTING METHODS AT GOLFDIGEST.COM/GO/FLAGSTICK.

WITH MIKE STACHURA