This is my understanding as well. Until recently, it wasn't worth the cost for most countries to secure their own supplies, so they just bought them from the co

This is my understanding as well. Until recently, it wasn't worth the cost for most countries to secure their own supplies, so they just bought them from the countries that sold them cheaply. When push comes to shove—or, when rare earth metals because strategic—it's a question of "do we want to invest in digging up our own?" not "gee, do we have enough of this stuff in the ground at all?".