At the time, how to make bagels was not widely available information. The union tightly controlled their trade secrets and shut down any shop that didn't work w

At the time, how to make bagels was not widely available information. The union tightly controlled their trade secrets and shut down any shop that didn't work with them. Membership was limited to family members of early members. Sounds like controlling the labor supply to me, though I understand that this is an opinion and others may disagree. All of this is material you can find fairly readily documented. Should that prove insufficient, I refer you to a 1913 essay by Booker T Washington: https://www.theatlantic.com/magazine/archive/1913/06/the-negro-and-the-labor-unions/529524/ https://www.theatlantic.com/magazine/archive/1913/06/the-neg... Choice quotes include: > One does not have to go far to discover the reason for this. In several instances Negroes are expressly excluded from membership in the unions. In other cases individual Negroes have been refused admittance to unions where no such restrictions existed, and have been in consequence shut out from employment at their trades. The essay details several specific instances. My point is not that unions are inherently exclusionary. My point is that they can be and occasionally have been put to that use, effectively limiting labor supply. Much like pre-unionism guilds often were.