getty Amazon reported that its annual Prime Day promotion (July 8 to 11) generated record U.S. sales this year, a reasonable brag in the context of a skittish consumer economy. But the real story about Prime Day—now ten years old—is how it has reshaped the retail landscape and how major competitors like Walmart have learned how to take advantage of the trail Amazon blazed. Prime Day has evolved from a one-company juggernaut into an industry-wide phenomenon with competing promotions from more than a hundred ...