Industry growth directly affects the intensity of rivalry among competitors. In periods of high growth, consumer demand is rising, and price competition among firms frequently decreases. Because the pie is expanding, rivals are focused on capturing part of that larger pie rather than taking market share and profitability away from one another. The demand for knee replacements, for example, is a fast-growing segment in the medical products industry. In the United States, robust demand is driven by the need for knee replacements for an aging population as well as for an increasingly obese population. The leading competitors are Zimmer, DePuy, and Stryker, but significant share is held by Smith & Nephew and Biomet. Competition is primarily based on innovative design, improved implant materials, and differentiated products such as gender solutions and a range of high-flex knees. With improvements to materials and procedures, younger patients are also increasingly choosing early surgical intervention. Competitors are able to avoid price competition and, instead, focus on differentiation that allows premium pricing.