Why is there a second ounce rate with the U.S. Postal Service?

The United States Postal Service, or USPS has a second ounce rate, or higher rate for mail compared to 1-ounce envelopes, in order to meet the fiscal demands of operations since the postal service does not receive tax dollars for operational costs and relies on postage proceeds to partially fund its operations. The USPS does offer free second ounce on automated or presort first-class mailings.

The USPS, in an effort to improve revenue, raised rates effective January 2014. The rate increase exceeded the annual rate of inflation. The Board of Governors chairman explained the higher increases are necessary in order to maintain the services of the post office, according to the USPS website.