請問甚麼是discount factor?

discount factor係計present value時用的
account有一個present value表
睇到不同年份,不同利率下的discount factor

因為今日的$1不等於明天的$1
因為可以存款得到利息

所以有之後年份預期cash flow要用discount factor去找出今天的present value

例如當利率是10% per annum
year discount factor
1 0.9091
2 0.8264
3 0.7513
4 0.6830

計算方法是 1 / (1+x%)^n
x係利率 n 係年份
eg.利率是10% per annum ,in year 4
1 / (1+10%)^4 = 0.6830

present value = cash flow X discount factor

這是一個金融術語。它是指將未來的貨幣轉換成當前或者其之前後，其貨幣的實際價值。它與累積恰好是相反的概念和過程。貼現也被叫做折現，也就是折合成現在的價值。
Discount factor
The discount factor, P(T), is the number by which a future cash flow to be received at time T must be multiplied in order to obtain the current present value. Thus for a fixed annually compounded discount rate r we have


圖片參考：http://upload.wikimedia.org/math/8/b/e/8be494f57e582ef894ead7c46de370a3.png

For fixed continuously compounded discount rate we have

P(T) = e − rT

discount factor=折扣因素