You may wish you had bought “Forever Stamps” when you had the chance, because postal rates are going up. The United States Postal Service has increased rates of not only stamps but also flat rate boxes and envelopes and other mail services. Postage for a one-ounce letter will increase ten percent, from 50 cents to 55 cents, but the price of each additional ounce has decreased from 21 to 15 cents. The nickel increase for a first-class stamp is the largest percentage hike since a four-cent increase occurred in 1991.