The world prices since 2/19/2013 are in RED and the US price is in BLUE.
Notice, of the most part, world prices are consisently above the US price but a crossover occurs between March 19th and April 19 of 2014. Then there is a significant diverence where the US price quickly outpaces the world price.
As of today (9/15/2015) the US price is at $3.00 lbs and the world price is about $1.25 (Source) so on the graph the RED world price line end point is the same but the US red line extends up to the $3.00 mark. The spread is even wider than what appears on the graph!
|Source: Haywardeconblog. Using historical data from HERE and HERE|