The Great Delivery Wars of the 21st Century continue as Walmart announced last week it will be offering free one-day shipping – without any membership fees – across 75% of the nation by the end of 2019.

More than 220,000 products will be available, and the shipping will be free on all orders over $35.

A recent CivicScience study found this announcement might just have a profound effect on American consumers, as nearly a quarter of U.S. adults said they will be “more likely” to purchase something from Walmart as a result of the one-day free shipping.

Amazon also announced, two weeks earlier, it was also rolling out free one-day shipping for Prime members.

In response to Walmart’s decision, Amazon took to Twitter, stating, “Others are trying to up their fast shipping game. Fact is, Amazon customers in thousands of cities across 44 major metropolitan areas already have access to millions of items with free SAME DAY delivery. Customers are smart – they know the difference.”

Amazon, as it turns out, may still need to keep an eye out on the competition, as Prime members still say they’d be “more likely” to try out Walmart. There’s not a significant difference between Prime users and account holders who don’t have Prime when it comes to how likely they are to shop at Walmart. 

Breaking it down by age, the under-35 cohort is 21% more likely to make purchases using free next-day delivery from Walmart than people over 35.

Walmart’s free next-day shipping seems poised to make its biggest dent in the suburbs, with 29% of suburban residents saying they’d be more likely to shop at Walmart.

And lastly, never underestimate the power of “free.” The following chart shows how important free shipping is to American consumers.

And when cross-compared with potential Walmart shoppers … well, the numbers are equally as impressive as all the other charts above. Even 12% of people who say free shipping is only somewhat important to them also say Walmart’s aggressive plans would make them more likely to make purchases there.

Clearly, the battle for shipping dominance is shaping up to be a major war in the retail market going forward. Walmart, in getting into the one-day shipping game, seems poised to dent Amazon’s current dominance, at least a little bit.