In the past 10 years, Walmart has opened 1,500 stores and its sales have increased by 50%, however it has only increased its workforce by 8% during this time. This minimal growth in the company's workforce explains the frequent complaints about insufficient shelf stocking and long checkout lines. These poor customer service reviews have resulted in weak sales growth. In 2015, the company hired 8,000 new department managers in an effort to rectify this issue.
See "Wal-Mart Scrimped on Hiring as Store Space Grew Rapidly", November 20, 2015