Restaurant workers in San Francisco are trying to change the equation on tipping.

Instead of the customer deciding how much to leave -- and restaurant patrons typically tip between 15 and 20 percent -- they are seeking to make mandatory a 25 percent service charge which would come with every bill.

Proponents of the change cite the difficult work restaurant employees do and the bad economy, which is driving down take-home pay for the wait staff.

Those opposed to the measure would point out that requiring a specific fee for service goes against the very concept of tipping.

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