SB Nation's chief hockey numbers guy Gabe Desjardin took a look at the USHL last week and how the league has grown in quality over the past few years.
It has some interesting graphs, including this one...
...which shows the USHL's production of NHLers going from scant to significant. He also points out that on a per-team basis, the USHL now produces as many NHL players as the CHL.