Some economic facts of life are obvious. You can’t take money out of a bank account unless someone has put money in it. You can’t get a rebate on a product if you don’t buy it. You can’t take advantage of lower interest rates if you don’t take out a mortgage. Only in Washington, D.C. can basic economic truisms be turned on their head. That’s the case with the expanded child tax credit. Less than a month ago, Mr. Bush signed a multibillion dollar tax cut that will issue checks of up to $400 to most middle-income families. The reimbursement...