As a general rule most movement will be horizonal not up or down. It all has to do with the swimbladder and how it is connected to the equilibrium of the fish and what a fish has to go through to change the swimbladder. I have watched LM bass follow baits on my depthfinder from 15 feet down around 5 -8 feet before turning off and coming back up but that is a temporary move to feed. I have seen largemouth in very clear water make an approx 8-10 foot rise to the surface to follow a swimbait but go straight back down within seconds. Deeper fish from my observation have a greater ability to move up and down as opposed to shallow fish and I suspect that is from water pressure being more consistant at deeper depths. I have watched Largemouth from both overhead walkways over ponds and lake and from underwater in extremely clear lakes for many days and they just don't move up or down that often or much. Most all of the movement is horizonal. Fish suspend over deeper water and move shallow at that depth when they become active to feed. Some that don't suspend hold to heavy cover and are just inactive. I have talked to Raplh Manns, who many consider to be one of the best biologists when it comes to bass, on the subject and he has noted the same thing as a diver observing bass as have others. Nobody that I know of has taken the time to do a true scientific study and have it published and reviewed by peers so there is no 100% sure on this in the scientific community.
As far as fishermen many believe that the fish move up and down because they catch fish in the middle of the day deep and in the afternoon shallow. Many bait fish like threadfin shad don't have the same limitations that a bass does. Threadfin have no swimbladder so they make fast movements up and down throughout the day. They form tight bait balls under bright conditions and scatter more in low light conditions as a general rule. The bait movement, not the movement of the bass, causes the good shallow bite in the am and afternoon and the better deepwater conditions through out the day.
I was never taught to bass fish by anyone other then what I saw on TV way back 20-30 years ago which wasn't much back then to lean from. So I came up with my own system and beliefs from overservation and what I learned on the water catching fish. I figured out the horizonal movement of bass in clear water lakes and have used it for probably around 20 years to catch fish. Many of my biggest fish have been caught suspended over deeper water midday after locating the bass shallow earlier in the day or week. I have also reversed it and found the fish with my depthfinder suspended over deep water and caught them when they moved into shallower water later at the same depth they were suspended at. So my whole system of fishing that I use is based on horizonal movements of fish and my belief that LM don't usually make large daily movements up or down.