Before 1981, assets used for the production of income were depreciable if they were subject to wear and tear or decline due to natural causes or obsolescence. Assets that did not decline in value on a predictable basis, such as land or stock, were not depreciable. Under the Accelerated Cost Recovery System, most real and personal property placed into service after December 31, 1980 are eligible recovery property. The system allows recovery of cost of depreciable assets at accelerated rates over periods shorter than their useful lives, with higher percentages in the early years. The cost of the property is recoverable over a 3-year, 5-year, 10-year, or 15-year period, depending on the type of property. Although the term "ACRS" is still used, accelerated depreciation is not available for real property placed in service after December 31, 1986, I.R.C. § 168(b)(3).