Parcel Post was abolished on 27 January 2013 and became "Standard Post".  Standard Post was abolished on 17 January 2016 and became "Retail Ground".  Rates remained unchanged
   

Old rates across country; 20-22%/year  price increase.
        20 lbs $26.23 in 2012; 34.58 in 2013; 38.21 in 2014, $45.67 after 31May2015
        70 lbs $71.84 in 2013, $105.83 in 2014; $127.93 after 31May2015
        Penalty rate ("dimensional weight rate") for girth+length>108", across country: $108.23 in 2012, 2013; $132.20 in 2014, $159.92
      
Zone creep: in 2014, low-cost zones 1,2,3 & 4 are declared not available unless you are required by law to make a surface shipment because you declare hazardous items like lithium batteries ("Price List, Notice 123, Effective January 26, 2014; Draft of 28Jan2014).  I
do not recall seeing this statement about those zones before.  You must use Priority Mail.

2012 - 31May2015: see above.
17Jan2016: rates unchanged
10April2016 rates unchanged by the "rollback" when the Postal Regulatory Commission ended the 2-year "exigent surcharge" of 2014.



BULKY OLD CHARTS

January 2013 ( file: ParcelPostZoneChart2013Jan.jpg)
ParcelPostZoneChart2013Jan  

31May2015, unchanged 17Jan2016, unchanged 10April2016     (file: ParcelPostZoneChart2015May31-2016Apr10.jpg  )
Zone Creep: Zone 9 added.  Zone Complexification:  Zones 1-4 unusable (use Priority instead) unless you are making a forced ground shipment due to dangerous cargo.
 

   ParcelPostZoneChart2015May31-2016Apr10.jpg