One chart that shows why Wal-Mart may want to buy a year-old start-up for $3 billion

Wal-Mart is reportedly in talks to buy a one-year old e-commerce startup for $3 billion.

Why would a giant like Wal-Mart spend $3 billion on a fledgling company like Jet.com? This chart gives you some clue.

Wal-Mart's e-commerce business growth has been decelerating while Amazon's has been accelerating.

Jet.com's founder Marc Lore has deep experience in e-commerce having founded Diapers.com's parent company, which he sold to Amazon. He's also been up front about his plans to take on Amazon.

Maybe he can fix this chart for Wal-Mart.

"Acquiring Jet.com would allow Walmart to become more competitive with [online retail] giants such as Amazon and eBay," said Michelle Malison, retail analyst at Euromonitor International, in a statement.

Based on the data released by Jet in July, the etailer has shown impressive topline growth, crossing a $1 billion run rate in gross merchandise value with more than 4 million shoppers on its platform, Euromonitor said. The company, which is still investing in its growth, is not yet profitable.

According to Recode, Jet is burning more than $20 million a month on advertising alone.

Jet's innovative pricing model, which adjusts the cost to shoppers as they add items to their cart, would "greatly assist" Wal-Mart with its own online site, Malison said. Jet has also made big strides in narrowing its delivery window to one day, which could give Wal-Mart an advantage, she said.

There's also the new customers Wal-Mart could gain. The start-up's focus is more on large urban metropolitan areas, while Wal-Mart's stronghold is more rural.

Despite its slower growth, Wal-Mart is the second-largest online retailer in the United States. Amazon is the largest.

(Notes on the chart: Wal-Mart reports digital growth on a global basis each quarter; Amazon's sales were calculated by Cowen & Co. analyst John Blackledge, who combined domestic and international revenue in its media and electronics & other general merchandise categories).

—CNBC's Courtney Reagan contributed to the reporting for this article