Lets say I have a preference for MMs over Skittles - a 2:1 preference. How often will I eat each? Probably in that ratio over a lifetime, because I'll eat snacks lots of times.
Now lets say I have a 60:40 preference for Driving a car as a career over being a shop assistant. What is the chance that the I will be a driver? Given I can only choose one, in a less than ideal world, it will be influenced by lots of things beyond my personal preference, opportunity most of all. But in an ideal world, the chance I am a driver starts to approach 100%, because why would I choose the 40% option, when I have a better one?
Free societies enable lots of choice, and tiny differences, 60:40 or even 55:45, will start to skew towards 100:0 over time. This is likely to play out right to the bottom, where people with fewer options are still likely to choose based on preference, hence garbage collectors and manual labourers vs shop assistants / PAs.
The consequence of tiny differences in preference and the small instances per person are likely to lead to some radical results.