NEW YORK — Superstorm Sandy knocked off nearly $4 billion of retail sales last week in the hard-hit mid-Atlantic and Northeast region, nearly 20 percent of the usual total, according to figures released Tuesday by a retail data service.

MasterCard Advisors’ SpendingPulse says Tuesday that the region, which accounts for about 24 percent of retail sales nationwide, typically generates $18.7 billion in sales for the week ended Saturday. But revenue came in at about $15 billion. The figures exclude auto sales.