This document discusses methods of calculating depreciation and obsolescence for property valuation. It describes four methods: straight line, constant percentage, sinking fund, and quantity survey. The straight line method assumes equal depreciation each year until the scrap value is reached. The constant percentage method uses a fixed annual percentage of declining value. The sinking fund method calculates depreciation as the annual sinking fund deposit plus interest. Obsolescence is reduced value from changes in fashion, design, or use.