The short version
Just 3 companies supply this market — thin enough that a single exit would be felt immediately. The price is down 25% over the past year, to $5.10 per unit. A shortage here was resolved within the past year — markets usually stay tight for a while after. Put together: worth watching — several of the pressures that precede supply trouble are present at once.
The numbers behind every sentence are on this page below — and the Watch button emails you when any of them move.