May 2007 Rate Change
The USPS has approved a rate change for May 14, 2007 in order to face rising costs. The new rate change is much different than any previous rate change. Instead of simply increasing postage rates based on mail class and weight, they are now calculating postage based upon the class, size, shape and thickness of the mail, in addition to the weight. These changes are being classified as Shape-Based Pricing.
USPS Shape-Based Pricing Initiative
The Shape-Based Pricing structure will create a more efficient mail system by aligning postage costs closer to actual postal processing costs. The USPS has stated that these changes will position themselves positively for future growth.

