Walmart Inc. WMT and Costco Wholesale Corporation COST are two dominant forces in global retail, each built on scale, efficiency and everyday value. Costco operates a membership-based warehouse club model,

But a big reason Walmart opts to close on Christmas Day boils down to employee morale. When workers are happy, it tends to lead to a more positive customer experience. That’s what Walmart wants. So it’s willing to forgo a day of profits during the year if it means ensuring that workers are content.

Worried you won't be able to send out a last-minute Christmas card? Here's what services run on Christmas Eve.