Why do you assume that demand for USPS mail is elastic? (at the current low price point anyway)

Right. So pedantry wins. The point is that there is some number of pennies after which the demand is elastic notwithstanding the original poster's indifference to a one cent price increase now.

What class of letter(s) would not be sent if prices went up?

The class for which there is only a marginal benefit to sending it in hardcopy vs. email. Or the class of items whose delivery could be delayed long enough to combine it with another item.

Yes, and what type is that? Got an examples.

Here are some types of letters that won't fall under that:

* Birthday/Christmas cards. The postage is a small fraction of the card. * Legal-y letters, (e.g. when you make an offical complaint ), since the price of the stamp is again a tiny fraction of what you're complaining about. * Big padded envelops of A4 print outs of contracts or something (again, postage is insignificant)

Most utilities are switching to electronic billing, and/or charging for paper billing, so they are already getting rid of postage.

What other post is that price sensitive?

Are you really arguing that the demand for first class mail is completely inelastic based on my lack of examples of what the marginal cases are? After some number of pennies of increase, demand will fall - are you actually disputing this?

All you're arguing is that there are some pennies of increase which could increase revenue. Fine. That's not saving the post office.