There are various reasons for discounting future benefits and costs. First, it is because of pure time preference where individuals incline to prefer the purchasing power present to that of the future even though the future could hold better rates. They normally tend to lean on enjoying the current benefits and costs compared to a future not assured of seeing. Also, the discounting of future amounts using constant high discount rates which could yield to low values. It is the opposite of the environment that believes that our descendants will acquire more wealth than we have. Lastly, low discount rates cause environmental degradation costs to shift to future generations hence reducing the incentives for environmentally favorable long-term projects. Even though some economists argue that low discount rates promote investments by allowing cheap bank loans but it is evident that these investments could be environmentally damaging. Therefore, a second filter is needed to ensure the sustainability of the environment.