The Margin: Sláinte, retailers! St. Patrick’s Day spending could hit a record $6.9 billion in the U.S.

Americans are expected to spend a record amount of green this St. Patrick’s Day.

The March 17 holiday that originally honored St. Patrick — who introduced Christianity to Ireland in the 5th century — has evolved to embrace Irish food, music and the Emerald Isle’s signature color. And Americans planning to celebrate are expected to drop a collective $6.9 billion this year, according to the National Retail Foundation. That’s $1 billion more than they spent on the holiday last year, and an all-time high since the NRF (the world’s…