A woman pushes a cart at a Costco store in Hackensack, N.J., in 2013. Big-box stores are effective delivery devices for fattening foods, economists argue in a new study. Ron Antonelli/Bloomberg via Getty Images hide caption

itoggle caption Ron Antonelli/Bloomberg via Getty Images

Customers in Bentonville, Ark., where Walmart's corporate headquarters are located, turn out for holiday shopping on Thanksgiving. Gunnar Rathbun/Invision for Walmart/AP hide caption

itoggle caption Gunnar Rathbun/Invision for Walmart/AP

A customer makes a purchase using Apple Pay on her iPhone 6 at a Walgreens store in Times Square last Monday. The mobile payment service has now been blocked by CVS and Rite Aid. John Minchillo/AP Images for MasterCard hide caption

itoggle caption John Minchillo/AP Images for MasterCard

A Bangladeshi worker participates in a protest outside a garment factory in Dhaka, Bangladesh, on Sunday. Hundreds of garment workers demanded better conditions. A.M. Ahad/AP hide caption

itoggle caption A.M. Ahad/AP

A shopper walks down an aisle in a newly opened Wal-Mart Neighborhood Market in Chicago. Jim Young/Reuters /Landov hide caption

itoggle caption Jim Young/Reuters /Landov

Cory Booker is mayor of Newark, New Jersey and honorary vice-chair of the Partnership for a Healthier America. Doug Van Sant hide caption

itoggle caption Doug Van Sant