How do you know what the supply is for services offered by people?  Or, what about future utilities yet created?  Can these be used to measure supply?  Imagine, time slots in a time share, or cell phones from a large batch.

Any individual can state to the registrar a commitment.  This is a commitment, by you, an individual, to deliver some amount of service, or amount of phsical utilities, over some period of time, which you can prescribe.

For example, you can promise to offer to cut up to 5 peoples hair in a day, if say, you were a hair stylist.  This is the limit upon which you FEEL that you are willing to do a day based on all the other commitments which you have given, either to the registrar or to your own life personally.  This would be representative of 5 'available hair cuts' in the system.