Increased job-mobility won't increase the number of higher paying openings though. Even if everybody at the bottom of the pyramid is laser-focused on making it up, the number actually succeeding won't really change, except perhaps through indirect effects. If anything, making people more content at the bottom would make it easier to raise for those who do want.
The number of people actually employed at minimum wage is quite small (usually low single digit percentage of total employment), though it does vary by location. If you add in some amount over minimum wage the number goes up (significantly), but if you add in tips and the like it goes down a lot. From what I've seen, the median amount of time people spend in that salary range is less than six months (of continuous employment).
