How were back-to-school sales at Walmart last month? Nobody knows for sure. - 

The government shutdown means no official economic data. But economist Chris Low tells Marketplace Morning Report Host David Brancaccio what we do know about back-to-school retail sales without the government's official report for September, or sales numbers from the nation's largest retailer, Walmart.

Follow David Brancaccio at @DavidBrancaccio