[Willie Green]

How could a coin possibly be any more efficient than paper money?

Paper dollars have an average lifespan of about 18 months.
They wear out fast with use.

Coins, OTOH, last on average about 30 years.

[Blackyce]

More efficient to make yes. More efficient to carry, NO. Over thirty years, paper costs you 30cents and a coin will cost 12. But, it wouldnt be worth the volume in weight for the banks to have to deal in metal. More importantly, it'd be less efficient for individuals. I carry almost no change now, and dont want to carry any in the future. A Better solution would be to alter the composition of the dollar to make it last longer.