hello everyone that Ken here, back with another video for you. As many of you
know or may not know my focus in my day job is in sports analytics particularly
in golf and today I'd like to talk a little bit about golf statistics and
specifically talk about the strokes gain metric that has been one of the
statistics that has absolutely revolutionized the game of golf and
there is still a reasonable amount of confusion around it so I'd love to go
through and explain my interpretation of it how it can be used and you know some
of the improvements that could potentially be made on it in the future
as usual please hit that like button if you enjoyed the video and if you'd like
to see more content like this please subscribe so for a little history lesson
strokes gained was created by Mark Broadie who is a Columbia Business School
professor I believe he specializes in finance computational finance and he had
this interest in golf and he recognized that golf in golf it was difficult to
compare shots apples to apples it was difficult to say hey a putt you know was
that a good putt compared to the quality of this Drive
so strokes gained helps us to tackle exactly that problem
it lets us compare shots apples to apples to each other this concept isn't
actually new in sports this was done in baseball previous to golf so instead of
comparing shots apples to apples and baseball you'd like to compare players
apples to apples and that can be difficult when they are playing
different positions so if you want to compare a picture to a shortstop how do
you do that and this wins above replacements that actually allows you to
compare them based on width and golf you're comparing these based on the
value of a shot now strokes gained has been incredible for golfers and and
their improvement because it lets people evaluate where they stand relative to
other players so the way we were able to calculate the value of individual shots
is basing it against a bet a benchmark or an aggregate so strokes gained is
calculated taking all the shots hit from a specific
distance or all the shots hit on a hole and seeing how your shot compares to
that benchmark this does depend on the sample or the pool they're using so
strokes gained as we know it is using only professional golfers data so if a
professional golfer hits a better-than-average shot they will have
positive strokes gained on that shot and if they hit a worse than average
shot they will have negative strokes game on that shot the best way to
explain this is by using an example so let's not think about the shots right
now let's think about an individual hole so let's say we have a par 4 on a golf
course and the average score on that hole for professionals is 4.1 so on
average it takes a professional golfer 4.1 shots to get it in the hole now if I
came along and I made a par I made a 4 that would mean that I picked up + .1
shots on the hole so I would have + .1 strokes gained on that
hole because I am playing at point .1 shots better than the average I'm
getting that much on the field if we do that for all 18 holes and we sum all
those up some some holes I might have a worse score so let's say it's a par-5
and the average score for the field is 4.5 and I make a 5 that means I lose 0.5
strokes to the field so if we add those up over the course of the whole round
you will have the amount of strokes that I've gained on the field over the course
of the entire round and then the same thing goes for the entire tournament etc
it can also go the other way where we're looking at the strokes gained not by
round or by tournament or a whole but by individual shop and that's where it gets
really interesting four strokes gained on a shot let's use the most simple
example possible from a ton of data collected we know that on a 10 foot putt
it usually takes the average professional golfer around 1.5 strokes
to get it into the hole so they almost they make it about 50% of the time
so if I were to make that putt that 10-footer that means that I would pick
up half a stroke on the field if I were to miss that putt assuming I didn't hit
it way by I would likely lose about a half a stroke to the field if you
aggregate all of the putts that you hit and then amount of strokes gained on
just those you'll get your strokes get into putting for the round or for the
tournament and you can extrapolate this out further and further so if we wanted
to look at an iron shot you see basically how far they are and how many
strokes that they are expected to make from that range based on where they hit
it you subtract how many putts that they're expected to take from that rain
from from the distance that they hit it from and they subtract that from the the
expected value and so through that you can go all the way back looking at
approach shots looking at tee shots and you can isolate each individual part of
the game you know this is really interesting especially when you're
looking at putting approach around the greens and driving because you can see
which players outperform the field in those areas and you can see for each
individual course what characteristics what elements of the game were most
important for scoring so strokes gained was initially calculated using dynamic
programming which means every time a new shot is recorded it would dynamically
update all of the shot locks after they got a certain amount of data that wasn't
necessary and it's all based on benchmarks so they know that a shot from
X amount of yards in a certain lie is a professional player is expected to get
the ball in the hole and a certain number of strokes so just like in a
putting example a 10 foot putt a professional golfer is expected to make
that in 1.5 strokes and that is what is known as the baseline or the benchmark
and everything is done based on that so I should note that strokes game is based
mainly on two factors so it is based on the distance and the type of lie so the
type of lie is is that in the rough is it in the fairway is it
correct cetera or is it on the green and the distance is based on on yards from
the pit well strokes game is a revolutionary
metric there still are a few challenges with it
that some I think will improve and get fixed but some will will always be a
challenge with this metric so the first thing is that the currently strokes game
does not take into account other factors than just distance and lie so if you're
looking at a putt there are some putts that are significantly harder than
others a downhill slider that's ten feet is going to be a lot harder than a
straight uphill ten footer and each putt is accounted for in the same way it's
just like a normal ten footer the law of large numbers suggests that that should
even itself out they should have roughly the same number of putts from those
different ranges but if you're looking at an individual golfer you're looking
at something in isolation that makes that value that you're getting
potentially skewed it also doesn't take into account wind or if your balls in a
divot or even the the different rough lengths of different courses each
individual course is normalized for the conditions but it isn't necessarily
normalized based on each individual lie and distance attribute so from my
experience strokes gained is a really valuable metric for comparing players
against each other but it has some challenges when you're comparing the
players against themselves because strokes gain is normalized against the
field the field strength is a huge factor in making that calculation and if
you're trying to compare one player tournament to tournament the strength of
field is going to have a significant impact on their performance you'll still
be able to understand general trend but if you're trying to look at strokes game
numbers as a you know a unit of comparison and you're trying to
understand magnitude that's going to be very difficult using this metric overall
I think strokes gained is of grilling a statistic
solves a lot of problems with the traditional golf statistics that we have
today where they're not necessarily meaningful
so for example fairways and regulation doesn't necessarily mean a whole lot one
relates to scoring or greens and regulation or the number of putts
these things are direct dramatically improved upon by strokes game on the
other hand I think strokes gain does have a ways to go to be the you know the
elite benchmark the number one metric in golf so thank you so much for watching
hopefully this is informative please let me know if you have any questions about
strokes gained in the comment section below as usual have a great one