GRJ I'm sorry I misquoted you, no offense, I was working from memory.
All diesels are 10.5:1. Most early Premier steam is 16:1. After 2001, MTH's engineers started looking beyond the Fisher-Price aisle... The 20-3047 Niagara and later 80" drivered Northerns were ~18:1. Medium-drivered locos with an idler gearbox, like Consolidations and Mikados are ~20:1. These are solid runners. Most RailKings until recently were 14:1 (RS-545 larger motor) or 17:1 (RS-385 standard motor). All of these ratios are "tall" (faster) compared to traditional norms for adult-oriented scale models.
I know for certain that some MTH steam locos with the tiny RS-365, such as RailKing train set locos and USRA 0-6-0 switcher, are geared lower-- 26:1, 28:1, and in some cases more. Dave Hikel's table confirms this (and he would know!)
Based on my personal experience with two different RK Mohawks and analysis of data in the sound files, it looks like MTH has begun using the 26:1 ratio in more of the RK steam locos with the RS-385. This is a good thing! I remember our discussion about the 1980s Williams brass. IMO 30:1 is about ideal, so the new ratios are a step in the right direction. Unfortunately, the great bulk of die-cast locos already made are geared too tall and require speed control for smooth operations at single-digit speeds.