Picket lines are a powerful means for workers to fight for their demands against their employers. They could be informational to get passers-by's sympathy. Or they could be on strike in a job action.

When the picket is related to a job action, the picketers are not working and do not receive wages. So the opportunity cost of their time is much lower than when they are working on their jobs.

But if the picket is informational only, picketers must give up their paid time to man the picket line. If someone else could man the picket line instead for a lot less than your hourly pay, it makes sense to outsource the picket. After all, that is the whole basis of the theory of comparative advantage¹. Namely, jobs should be allocated to those who can do them at the lowest opportunity costs.

Exactly this kind of economic reasoning is behind the rent-a-picket arrangement organized by the Mid-Atlantic Regional Council of Carpenters. The 30-man strong picket line outside a bank in downtown Washington, D.C. was protesting the low wages paid by a construction firm to workers renovating the bank. If the carpenters can earn $25 an hour on the job and the homeless picketers are happy to make only $8 an hour picketing, renting a picketer can save ($25 - $8 = $17) $17 an hour.

But would the moral force be reduced if one is not willing to put one’s whole wages on the line to picket for one's cause? We could, of course, pose the same question for enlisted armed forces vs ones based on universal draft.