Wal-Mart ( WMT 0.83% ) shares rallied about 13% this year on the strength of its turnaround efforts, easily outperforming the Dow Jones U.S. Retail Index's 3% gain. But now that the stock is hovering in the $70s, investors might be wondering if the retail giant will split its stock soon. Let's look back at Wal-Mart's stock split history to see if that could happen in the coming year.