Bill Phelps, co-founder and chief executive officer of the California-based Wetzel's Pretzels franchise, was a prominent advocate for the Golden State's $15 an hour minimum wage for several years, but has recently changed his opinion.

He now says that the rate — which has only just reached $11 — is already squeezing his businesses and hurting workers, and he worries things will likely get worse as minimum wage rises to the $15 level.

"We've had a 38 percent increase in the minimum wage from 2013 to now. They're looking at another 35 percent increase in the minimum wage over the next four years. I think the past increases have been good for employees, our employees, California employees. I think the next increases are going to be bad for employees. I think it is pushing it too far, too fast and I think employees will be hurt by those increases," Phelps said at a little-seen forum held by Claremont-McKenna College in late March.

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