CWL has it right,but there's more...
Shotgun effectiveness depends on multiple hits. At any distance further than contact distance, both hits and energy drop dramatically.
At 35 yards, #7 1/2 shot that left the muzzle at 1150 FPS are doing less than 800. #4, maybe less than 900.
As a long time dove shooter, I've been sprinkled with small shot fired from around 125 yards. Of course, I wore protective glasses and a hat. The little shot there didn't even sting.
A gun/choke/load combo that prints into 30" at 25 yards will have a "Pattern" much larger than 120" at 100 yards. Deformed shot and loss of velocity will scatter the shot over half a Zip Code.
In his master work, Brister mentions his wife saying,"Just tell them Improved Cylinder choke goes to H*ll gradually, Full all at once".
So how far does the pattern remain effective?
Not far at all. Except for the best loads and the ebst luck, darn near all patterns sre too thin or have insufficient energy to do anything over 55 yards....