Economics. At the other end of the spectrum are economic drivers in which take-back programs create clear economic benefits for customers. Dell's Asset Management Program can provide economic benefits to customers. Ernst & Young uses Dell's direct leasing program, which in one year supplied the company with 20,000 laptop and desktop computers. US tax law requires that computers be depreciated over five years, yet most firms use equipment for just two to three years. As a result, computers often sit on the books, requiring continued payment of property taxes on the equipment, and generating storage costs. Companies can also pay $300 or so for their disposal. Avoiding these costs meant substantial savings for Ernst & Young, as well as environmental benefits. Under Dell's leasing program, after 24 months, older computers can be returned to Dell, who, in turn, refurbishes or recycles them. Economics plays a part in other take back programs such as Hewlett Packard's toner cartridge take back program.