“Amazon has just built up its reputation around rapid fulfillment incredibly well,” Mr. Carlborg said. “Customers really trust Amazon’s fulfillment offerings.”
Those shoppers include Carissa Vinovskis, 26, who puts in 12-hour days researching diabetes at Children’s Hospital Colorado. She used to shop for Christmas gifts in stores, but as she got busy with graduate school and later her job, she had less time and patience.
Panic set in fast in the middle of this month when Ms. Vinovskis realized she had just six days to get presents before visiting her parents. She found a few cute things on Etsy — “beautiful, handcrafted gifts,” she said — and then realized they would take about four weeks to arrive.
“I was like, welp, Amazon Prime it is!” she said.
An Amazon spokeswoman pointed to a statement in which the vice president who runs Prime, Cem Sibay, said, “We keep working to add faster and even more convenient delivery options.”
Amazon’s speedy delivery has been a key focus. In 2000, it invested $60 million in Kozmo, a New York start-up that delivered snacks, movies and other goods in less than an hour. About a year later, Kozmo shut down. But it remained an inspiration to Jeff Bezos, Amazon’s founder and chief executive, according to a former Amazon employee who heard him discuss the matter.
Mr. Bezos saw that quick delivery could change how people buy things. Price and selection have always been important in retailing, but delivery would surpass store location as another critical factor.
In 2005, Amazon began offering free two-day shipping for Prime members, which Consumer Intelligence Research Partners estimates covers more than two-thirds of households in the United States. Almost a decade later, it started Prime Now, which delivers goods in as little as an hour in 30 cities.