In the table published at this U.S. Postal Service Website, USPS compares different service classes in different aspects. One aspect is called "incentive". I wonder what it means? From Google, I guess it may mean "A payment or concession to stimulate greater output or investment", but this meaning doesn't explain the aspect in the USPS table well to me.
It refers to discounts applied for certain classes of customer participation, be it volume or voluntary technological compliance (USPS barcode labelling, etc.)
Generically, the USPS defines "incentive programs" to mean:
That said, after looking through the links provided in JLG's comments, browsing some USPS websites, and talking to my cousin last night (who works for the USPS), I can't find any incentive program other than the one that gives a 2% discount if registered business customers use barcodes on their mailings. (Intuitively, such a discount would make sense, as the barcodes would reduce USPS labor costs by allowing the envelopes to be sorted via automation, rather than by hand.)
However, a USPS website says:
Stamps.com mentions up to four ways an envelope can be barcoded:
but I'm not sure if any of those barcodes would lead someone to "a webpage that allows the recipient to purchase a product or service on a mobile device, or a personalized URL, which leads to a web page that is unique to an individual recipient," causing me to wonder if any of those barcode(s) would qualify a registered business customer for the discount.
I don't believe any volume discount applies when referring to "incentives" in this context. The USPS does offer bulk mailing rates, but I don't think that falls under "incentives" in the table at the O.P.'s website.
Moreover, incentive programs don't seem to be run year-round; the one mentioned above ends at the end of August 2012.