For Costco, treating workers well has led to increased motivation, higher quality service, greater productivity and lower turnover. After the first year of employment, turnover was less than 6 percent, one of the lowest rates in the industry. The combination of good wages and the knowledge that there were opportunities for advancement was an important incentive for employees to work hard and build a career with the firm. The high quality of service provided by motivated, engaged employees at Costco, combined with the low prices, meant that customers returned and were willing to pay the membership fees. Costco’s high-quality service also attracted a clientele that shopped not only for basic goods but also luxury items, which were still more profitable, even with the low markup. As a result, Costco had higher annual sales per square foot than its most direct competitor, Wal-Mart’s Sam’s Club, ($795 versus $516), and higher annual profits per employee ($13,647 versus $11,039) even though Costco’s average wage was 42 percent higher. Over 16 years, Costco grew from 206 warehouses and $16 billion in sales to 554 warehouses and $69.9 billion in sales.