原级：perpetuity
1. 永续年金：当发生非线性变化时,就要用到凸度(convexity)这个概念,它的意思就是利率变化是如何影响债券久期的. 6.永续年金(perpetuities)与年金(annuities)那个一个正常的计息债券就可以分成一个贴现的本金(redemption)与年金,Cn是固定的coupon:
2. 终身年金：perfectly inelastic 完全无弹性 | perpetuities 终身年金 | physical capital 物质资本,实物资本
1. The present value of this annuity is, therefore, the difference between the values of the two perpetuities
所以，这个年金的现值是这两个永续年金价值的差异
2. In other words, the difference between the two perpetuities is an annuity of C for t years.
换句话说，这两个永续年金的区别就是 t 年的年金 C 。
3. The only difference between the two perpetuities is that the first one also provides a cash flow in each of the years 1 through t.
这两者之间的唯一区别是前者也提供了一个从1年到 t 年每一年的现金流。
4. Both perpetuities provide a cash flow from year t + 1 onward.
两个永续年金都提供了一个从 t + 1年开始的现金流。