NEW YORK (TheStreet) -- On Wednesday, Wal-Mart(WMT) - Get Report shares had their worst day in fifteen years. The stock fell 10% to $60.03 following the company's announcement that revenue and profit would continue to drop through 2017 as it invests billions in higher wages and improving its online operations.

But it wasn't merely a one-day stock decrease. As of yesterday, Wal-Mart shares were down 30% for the year.

And according to Wells Fargo analyst Matt Nemer, this poor performance is a direct result of Amazon's(AMZN) - Get Report  influence.

Amazon has changed the way consumers view retail, shifting sales to more direct channels, Nemer wrote in a research note Thursday morning entitled "WMT: The Great Omnichannel Tax."

"Walmart is leaning in to this shift (new mobile apps, expanded online selection, faster shipping, and grocery pick up) but these channels have an inherently lower margin because they add variable expenses like order picking, freight, store labor and higher returns," Nemer wrote. "It is best for Walmart if customers drive to the store, browse, fill their own basket, and handle the 'last mile' in the trunk of their Chevy."

According to Nemer, Walmart's trying to capture new customers and get them to shop more frequently, but "it remains to be seen if this will outweigh the declines in existing customer lifetime value."

And while Wal-Mart may attribute their upcoming losses to investments in innovation and e-commerce, Nemer views these costs more as a tax that comes from trying to compete with Amazon.

Take the investment it takes to compete with Amazon on logistics. Wal-Mart unveiled a shipping pilot called ShippingPass in May to try to combat Amazon's success with Prime. But these initiatives are pricey.

In 2014, Amazon disclosed it paid "billions of dollars for Prime shipping and invested $1.3 billion in Prime Instant Video." These kinds of programs also require a level of agility that can be hard at an established, traditional organization like Wal-Mart.

"I do not believe Wal-Mart operates at Internet speeds, so it takes a large organization to gather momentum to launch new services," Needham & Co analyst Kerry Rice said in an interview earlier this year.

Wal-Mart also tried to compete against Amazon's Prime Day this year by offering its own sales. But slashing prices is certainly a tricky way of maintaining a business.

Retailers that are threatened by Amazon may want to compete on prices, but that's not a perfect solution, said Vikas Mittal, a marketing professor at Rice University's Jones Graduate School of Business. "They're not going to be competitive if they try to become yet another Amazon," he said. "They'll have to find something that differentiates them from Amazon."