From Slate.com, regarding the USPS’ new “forever stamp” that you can buy today and use whenever you want regardless of what happens to postal rates in the future:

The 20-cent stamp from 1981 would be equivalent to 45 cents in today’s dollars—which makes today’s rate 10 percent cheaper than it was 26 years ago. Should this historical pattern hold, you’d be paying more for today’s forever stamps than you would for any stamp in the future, no matter how high the rate goes.

So how long until postage is free? Had I been paying attention in school, I could answer that.

Via Kottke.