With the slow down of the US economy cargo loads have also dropped as the US is not importing as much as in the past from Asia. Cargo rates are currently at a 20 year low from the Far East.
As a result many cargo carriers including Polar have adjusted their Asia flight schedules.
Polar has reduced its US - Australia service from 4 times per week to 2 weekly flights. These planes then operate up to Hong Kong before heading back to the mainland US via Anchorage.
I think you will notice also in HKG that Cathay Pacific along with Air Hong Kong have more than the usual freighters sitting around not doing much.
From the desert to the sea, to all of Southern California