“It’s a very regressive proposition because it means the more you do, the more benefit you get,” he said. “You shouldn’t favor the small number of tipped workers who make more than $50,000 or $60,000 a year. You should think about favoring the low-wage and low-income tipped workers who make maybe $20,000 or $30,000 a year.”

It is also difficult to predict how potential tipsters would react to the knowledge that tipped workers are exempt from income tax. The Tax Foundation, a conservative think tank, raised the prospect that some employers would find it more profitable to switch to tip-based wages. Lawmakers could theoretically write a provision to ensure that high-paid workers like lawyers or doctors don’t start earning a portion of their income as voluntary tips, but none of the measures introduced in Congress currently include those safeguards.

Gleckman was also concerned that tipped workers would begin to see lower tips, giving the example of a warehouse worker visiting a restaurant. If the warehouse worker knows that she makes about the same amount as her server but the server does not pay the same income tax, the warehouse worker may be less inclined to leave a generous tip at the end of a meal.