Walmart (WMT) and Target (TGT) have been fiercely competing for US consumers' dollars. Walmart has been winning this battle so far this year, especially on Wall Street, where the retail giant's stock is up 57% year to date, while Target's is up only 6%. But the reason for that gain may surprise you.

In the video above, Yahoo Finance Senior Reporter Brooke DiPalma explains how Walmart has gained the upper hand.

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This post was written by Stephanie Mikulich.