How expanded child tax credit aided these moms, changed economy

Many social welfare programs target specific forms of assistance for specific groups. The expanded child tax credit last year became a test of a different model: cash assistance for families, with no strings attached.

Over the summer, Danette Mahabeer had a problem familiar to most parents at one point or another: Her daughter, Soheila, was “sprouting,” Ms. Mahabeer says. “Growing out of everything she owned.”

Clothes that fit were suddenly tight. So was money. As for food, Sohelia was ravenous.

For Ms. Mahabeer, a single mother in Nashville, Tennessee, increased...