I think it is reasonable to assume that only a percentage of the experts will be willing to quit their job and move to a new one. People have all sorts of reasons to stick to current jobs!

Everyone has a price... If there are experts out there that fit your need but you can't attract them because you aren't paying enough then you should increase your offer. Supply will meet demand.

Businesses don't have infinite resources to hire workers, and most workers old enough to truly be experts are not going to relocate easily. 1x, 2x, even 3x market wages won't be enough to move someone that's already earning a comfortable wage, likes their job, and has roots (a home, a spouse that likes their job, children in school, family nearby) in their current community. No single digit multiple of market wages would get me to move to Silicon Valley, let alone the middle of West Virginia.

Luckily, you are just one person. Here, we're speaking about an entire market. And yes, 2x and 3x market wages would absolutely cause major shifts in labor. Even < 2x market wages would accomplish this. It already happens the other way, 1.5x and 2x market wage multiples drive flow of skilled engineers from California to Wall Street.

"For one thing...the pay is often too low."

Sounds like something pretty easy to fix.

That is the central debate isnt it? The market fix is to increase wages until "shortages" disappear. The disingenuous fix is to claim there is a "shortage" and import workers to broaden the supply. That is great for hard-working foreign workers, but sucks for the domestic graduate pool that has a higher standard of living -- most Americans simply will not raise a family in a shared 2br apartment -- while that is common for immigrants. So they will instead seek better pay in other industries.

This is all fine, but it is disingenuous to claim shortages when the real problem is a refusal to pay market wages.

Raise labor prices and you'll get qualified candidates.