From Dave T:

Around 1990, Tom & Jeff Summit co-authored the Dynacraft book "The Modern
Guide to Shaft Fitting". (The copyright date is 1992, but the
research had been going on for a couple of years at that time.)

The book presents a couple of interesting conclusions:

(1) There is not much range in bend points: less than an inch from
highest to lowest in steel, and less than 2 inches in graphite.

(2) One inch of bend point is worth about one degree of launch angle.
(This was cited from another study made by a shaft manufacturer.)

So the most trajectory difference you could expect would be under 2 degrees.

BUT...
Graphite shafts were rather in their infancy at the time of their
research. Shaft manufacturers know a lot more about how and where to
place "hinges" in the shaft. The overall profile is more complex than
just a measure of bend point (as defined in the book). I know I have
seen more than a 2* difference in launch angle from shaft to shaft,
with the same head and the same golfer. (It was not robot testing, so
I can't be dead certain that it wasn't a subtle change in the
golfer's swing -- in response to a difference in feel. But I have no
evidence that the swing had changed.)
From Tom wishon:
Back when Jeff and I did the work for the Shaft Book I wrote, the industry knew nothing about bend profile and relegated all their expressions of how a shaft could bend differently and thus have an effect on launch angle/traj through this measurement they invented called bend point. If you remember, this involved pushing both ends of the shaft toward each other and finding the apex of the curve created. When you make tubes that all have to be .58-.60 on one end, and all have to be either .335 or .370 on the other end (tapered woods were dying and almost dead in 1990) and all have to be about the same raw length, such a test cannot reveal much than a 2 inch difference in the apex. We know that now, but we didn’t then, so we just duplicated the bend point test the shaft makers were all using at the time. Today, it’s interesting that some companies and a lot of individuals still talk about bend point on shafts when it has become quite worthless for ever trying to describe how one shaft can have a different distribution of stiffness over its length vs another.

I first became curious about this back in about 1994 when a graphite shaft company from Finland called Excel Composites debuted a line of three different wood shafts they marketed to have the same butt stiffness but which each displayed a different flight characteristic. Only knowing about butt frequency or deflection board measurements at the time, trying to think about how to SEE these differences in these three Excel shafts was what prompted me to do freq measurements at different clamping positions on the shaft. While these were not that great for being able to see what I really wanted to see, they at least did offer a rudimentary beginning way to at least see that some shafts did have a different distribution of stiffness over their length. And then from that eventually came the way we do this now – which as you know we admit is not real stiffness but still gives us what I believe to be a decent way to COMPARE shafts for the purpose of being able to predict bending feel and flight characteristics.

I certainly can’t and don’t spend as much time noodling in this as I would like these days – lots of things on the To Do list all the time prevent that. I recognize there is a lot more to this than meets the eye when it comes to really opening the door for truly accurate and meaningful empirical ways to define shaft stiffness fitting and performance for all different types of golf swings. Anyway, we at least know a heckuva lot more than we did 20 yrs ago and a lot of that really has helped us be a little better in matching each golfer swing type to a shaft that performs as well as the swing type can generate from the shaft. I tend to doubt that shaft fitting will ever be 100% cut and dried perfect simply because of the golfer feel preferences/dislikes which are such an important part of shaft fitting for certain golfer types. But at least we’re a lot better at it than we were in the past, and we do understand a lot more in terms of what the shaft actually can do as well as cannot do.

TOM