Who the minimum wage actually helps

Econlib's David Henderson notes how the benefits of minimum wage doesn't actually help very many of the poor (via Greg Mankiw):

If the federal minimum wage were increased to $9.50 per hour:

• Only 11.3 percent of workers who would gain from the increase live in households officially defined as poor.
• A whopping 63.2 percent of workers who would gain were second or even third earners living in households with incomes equal to twice the poverty line or more.
• Some 42.3 percent of workers who would gain were second or even third earners who live in households that have incomes equal to three times the poverty line or more.