EPDM systems have been on the United States commercial roofing market since the 1960s. Their widespread use began in the 1980s, and the technology has developed a favorable market share in the industry since that time. Their rise in market share correlated with the energy crisis in the United States during the 1970s (which drove the price of bitumen up due to higher oil prices), the development boom of the 1980s and increasing roofing labor shortages. The size of the membrane sheets (typically 20 feet by 100 feet) allowed contractors to install the systems with less labor and virtually no equipment. These factors quickly contributed to their widespread acceptance, as they were more economical to install over the labor-intensive, equipment-laden built-up roof systems.